Content:

SSP – Stratigraphy, Sedimentology & Palaeontology

SSP1.1 – Open session on stratigraphy, sedimentology and palaeontology

EGU2020-748 | Displays | SSP1.1

Glacio-eustatic variability in the sedimentation pattern over northern Japan during the past 600 ka

Sushree Sova Barik, Raj K. Singh, Pratik K. Upadhyaya, Lisantaraj Biswal, Nishant Vats, and Manisha Das

The Japan Sea is a semi-enclosed marginal sea affected by global sea-level fluctuation, expansion of seasonal and permanent sea-ice cover, having a significant influence on the regional climate neighboring Japan Sea. Middle Pleistocene to Holocene sediments of the Integrated Ocean Drilling Program site U1423 situated in the northeastern part of Japan Sea was processed for the grain size analysis, semi-quantitative mineral analysis, and clay mineral analysis to access glacio-eustatic control on sedimentation pattern over Japan Sea during the past 610 ka. The average time resolution per sample is ~10 kyr. The mean grain size data suggest the dominance of silt size fraction over the sand and clay. The end member modeling of grain size data suggests the presence of two different energy conditions that varied with the time and influenced by the glacio-eustatic changes over the Japan Sea. The grain size data are relatively coarser and deposited in the higher energy condition during the glacial periods in comparison to interglacial periods except for MIS 2, 4, and 8. The higher energy condition during the glacial intervals suggesting deposition of grains due to the melting of seasonal/permanent ice sheets in the northern Japan Sea. The eolian dust brought from the Chinese loess deposits are relative finer in size and dominated by a higher proportion of quartz. During the glacial phases, illite and kaolinite (%) show a decreasing trend than the interglacial phases suggesting less terrigenous input. The high illite and decreased smectite (%) during interglacial phases suggest a higher degree of physical weathering. The significant increase in the smectite/(illite+chlorite) ratio suggests a higher degree of chemical weathering of the nearby source area, which varied over time. The overall study suggests the phase-wise variability in the presence of permanent/seasonal ice sheets and East Aian Winter Monsoon strength during the past 600 ka.

How to cite: Barik, S. S., Singh, R. K., Upadhyaya, P. K., Biswal, L., Vats, N., and Das, M.: Glacio-eustatic variability in the sedimentation pattern over northern Japan during the past 600 ka , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-748, https://doi.org/10.5194/egusphere-egu2020-748, 2020.

EGU2020-21991 | Displays | SSP1.1

Cosmogenic-nuclide burial ages for Quaternary drilling core sediments in the Yangtze River De, China

Xiao Qi

EGU2020-13000 | Displays | SSP1.1

On the application of confidence limits to biostratigraphy: an example from diatoms

Cristina Lopes and João Velez

For years, diatom-based biostratigraphy has been settings bio-events based on a qualitatively approach. This means that the biostratigraphy would set an age based on the findings or not of a certain species. However, how many species are needed to consider a certain datum as certain? One, ten, 100? Moreover, each biostratigrapher sets its on limits. One might consider one as enough and another 10. Therefore, the scale more often used is the absent, rare, frequent, common, dominant or abundant with an explanation of what of these definitions mean. This is very common in, for example, IODP expeditions.

However, what would happen to these biostratigraphy levels if one would apply, for example, a concept of 95% confidence level? Moreover, what would happen to an age model if this concept would be applied to all the biostratigraphy microfossil?

Here we will show Expedition 346 age model differences with and without confidence levels applied to diatoms. The differences can be significant and even considering the existence of a hiatus can be reconsider if confidence limits are applied, turning a possible hiatus into a very slow sedimentation rate having serious implications to the initial paleoceanographic interpretations.

How to cite: Lopes, C. and Velez, J.: On the application of confidence limits to biostratigraphy: an example from diatoms, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13000, https://doi.org/10.5194/egusphere-egu2020-13000, 2020.

EGU2020-11213 | Displays | SSP1.1

Scarce population of malacofauna from MIS8/L3, at Titel loess plateau, Serbia

Milica Radaković, Bojan Gavrilović, Luka Bosnić, Milivoj Gavrilov, Pal Sümegi, David Molnár, and Slobodan Marković

We present our preliminary findings from the survey of malacofauna of the Titel loess plateau – Mošorin site (Serbia), conducted during 2018/2019. Titel loess plateau is situated near the confluence of Tisa and Danube rivers, in the southern central part of the Vojvodina province, the region known for having valuable continental climate record for the past million years. The study aims to gather palaeoenvironmental data and discern patterns of environmental changes during the Pleistocene in the loess domain. Previous surveys were done at the loess sites in Batajnica, Zemun, Crvenka and Irig. The exposed part of the Mošorin loess-paleosol section is 30 m high and covers the last three glacial periods. It is the first time we carried out a malacological analysis on the L3 segment of the profile. A total of 26 samples were collected from 5.2 m long cleaned profile section (ending of S3 to the beginning of S2). Nine species of snails were present in this horizon, including Chondrula tridens, Granaria frumentum, Helicopsis striata, Pupilla muscorum, Pupilla triplicata, Punctum pygmaeum, Succinella oblonga, Vallonia costata, Vitrina pellucida, and certain as-yet-unidentified slug taxa (Limacidae, Agriolimacidae, Milacidae). Greatest diversity and abundance was found near the S3 paleosol. Samples with no snail shells are continuous, and they are situated in the middle and upper part of the studied profile section. The first three samples that are closest to S3 include 65% of all snails shells found in the profile. The number of snail taxa and their abundance gradually increases again toward the S2 paleosol. Based on ecological preferences of discovered species (mostly thermophilous and xerophilous) we deduced that the environment during the L3 time period was an opened grassland, while the climate was mild and mostly dry.

How to cite: Radaković, M., Gavrilović, B., Bosnić, L., Gavrilov, M., Sümegi, P., Molnár, D., and Marković, S.: Scarce population of malacofauna from MIS8/L3, at Titel loess plateau, Serbia, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11213, https://doi.org/10.5194/egusphere-egu2020-11213, 2020.

Micropaleontological and isotopic analyses were performed on 93 samples covering the first 50m of borehole U1460 in aim to reconstruct the paleo-environmental and paleo-climatic conditions of western australian shelf. Borehole U1460 was drilled at a water depth of 214 m during IODP (International Ocean Discovery Program) 356 expedition.

The distribution of benthic foraminifera and ostracod assemblages associated with planktonic foraminifera variation allow to characterized two main climatic phases : one dominated by generally cold conditions (glacial-like, from 50 to 20m) and another interglacial-like phase (from 20 to 0m), characterized by warmer climate. Those have been identified on the basis of distribution of tropical warm water Goloborotalia menardii (planktonic foraminifera) that shows high abundance only from 20 to 0 m, attributed to the interglacial-like phase, coherent with δ18O values curve.

The glacial assemblage is composed by an assemblage dominated by ostracod genera/species such as Pterigocytherei ssp., Krithe spp.,Argilloecia sp., Pseudocythere caudata, Trachyleberi ssp. and by benthic foraminifera such as Cibicides lobatulus, Elphidiumsp., Hyalineasp., Rosalina bradyi. These assemblages indicate cold bottom conditions with probably poorly oxygenated and organic-rich sediment environment.

The interglacial assemblage is characterized by ostracods species as Neonesidea sp., Bradleya sp., Cytherella sp., and by benthic foraminifera as Meloni ssp., Uvigerina spp., Quinqueloculina sp., Textularia sp., Trifarina sp., Cassidulina sp., Brizalina sp., Bulimina sp., Sigmoilopsis schlumbergeri. This assemblage suggests warm bottom conditions under well-oxygenated, high energy regimes and food input that would be important.

Those two phases include probably multiple glacial and interglacial stages but the most spectacular result indicates that after the onset of MIS12, one of the major glaciation in the Quaternary), the oceanographic conditions in the Western Australia sector changed deeply, either because of oceanic current re-organization or because of the continental climate change (dry/wet climate transition) that controls the amount of micronutrient input into the ocean.

How to cite: Angue Mintoo, C., Courtillat, M., and Bassetti, M.-A.: Paleoceanographic variations in SE sector of Indian Ocean (Australian shelf, IODP-U1460 site): is the MIS12 the trigger for long-term oceanic circulation re-organisation? Insights from benthic meiofauna (ostracods and foraminifera), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22609, https://doi.org/10.5194/egusphere-egu2020-22609, 2020.

EGU2020-425 | Displays | SSP1.1

Chemical evidence for the preservation of collagen in Eocene turtle shell using Py-GCxGC-TOFMS

Raman Umamaheswaran, Suryendu Dutta, Hukam Singh, Sumit Kumar, and Ashok Sahni

Studies on organic preservation in fossil tissues have been a contentious topic, as fossils have been thought to preserve little, if any, organic content after diagenesis. Several studies have previously reported the presence of collagen in fossils from deep time including in Cretaceous dinosaur bones (e.g.: Schweitzer et al., 2007, Science v. 316, 277-280). These findings have also been the subject of criticism with respect to the reproducibility of their results (e.g.: Buckley et al., 2017, Proceedings of the Royal Society B v. 284: 20170544). In the present study, we analysed a turtle shell from Eocene to ascertain a suitable proxy for the preservation of collagen, by using comprehensive pyrolysis gas chromatography – time-of-flight mass spectrometry (Py-GCxGC-TOFMS) and comparing the pyrolytic products obtained to those of modern turtle shell and collagen standard. 

In order to add to the robustness of the study, industry standards of chitin, melanin and collagen were analysed using Py-GCxGC-TOFMS and their chromatograms compared for characteristic pyrolytic products that can be used to differentiate between them. Collagen could be differentiated from the other nitrogen-bearing biopolymers based on the presence of characteristic cyclic dipeptides known as 2,5-diketopiperazines (DKPs) which are formed by the recombination of peptides during pyrolysis. We compared the chromatogram of collagen standard to that of a modern turtle shell and found that the two chromatograms could be correlated based on the presence of diketodipyrrole, 2,5-DKP(Pro-Pro), 2,5-DKP(Pro-Ala), 2,5-DKP(Pro-Gly), 2,5-DKP(Pro-Hyp), 2,5-DKP(Pro-Arg) and 2,5-DKP(Pro-Lue/Ile). We then compared the chromatogram of modern turtle shell to the Eocene shell and confirmed the presence of diketodipyrrole and 2,5-DKP(Pro-Pro) in the fossil shell thus unambiguously indicating that collagen is preserved.

How to cite: Umamaheswaran, R., Dutta, S., Singh, H., Kumar, S., and Sahni, A.: Chemical evidence for the preservation of collagen in Eocene turtle shell using Py-GCxGC-TOFMS, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-425, https://doi.org/10.5194/egusphere-egu2020-425, 2020.

EGU2020-1466 | Displays | SSP1.1

Life and Death in the Jurassic Seas of Dorset, Southern England

Malcolm Hart, Gloria Arratia, Chris Moore, and Benjamin Ciotti

There are very few examples of predatory behaviour by coleoids in the fossil record (e.g., Jenny et al., 2019) and, in the known cases, the victims are always fish. The examples described by Jenny et al. (2019) involve Clarkeiteuthis conocauda (Quenstedt, 1849) from the Toarcian (Jurassic) Posidonienschiefer of Southern Germany and the capture of fish assigned to Leptolepis bronni (Agassiz, 1832). In all the described examples, the fish appears to be held in the arms of the coleoids: arms which are identified by the lines of hooks preserved in the position of the arms.

The Jurassic succession of the Wessex Basin, especially that cropping out along the Dorset Coast, contains important Lagerstätten for squid-like coleoid cephalopods. The Blue Lias and Charmouth Mudstone formations have, since the nineteenth century, provided large numbers of important body fossils that inform our knowledge of coleoid palaeontology. In many of these mudstones specimens of palaeobiological significance have been found, especially those with the arms and hooks with which the living animals caught their prey. This is particularly true in the case of a specimen in the collections of the British Geological Survey (GSM 87477), identified, as Clarkeiteuthis sp. cf. C. montefiorei (Buckman, 1879), which was found in the nineteenth century from an un-specified location near Lyme Regis. This specimen is seen to have a fish, identified as Dorsetichthyes bechei (Agassiz, 1837), being held by two arms that are positioned on each side of the fish which is aligned with the jaws of the ‘squid’.  The bones in the head of the fish are broken in a manner that suggests a quite violent attack, and not simple crushing during burial and taphonomy. While the fish is damaged in ways that are suggestive of it already being dead, has the ‘squid’ choked to death, or was its death the result of sinking to the sea floor and being overcome by, for example, reduced oxygen conditions in the water column? Whatever the cause of death this unique specimen and is the oldest that shows a direct feeding attack by a ‘squid’ on a fish that was ca. 200 mm in length.

Jenny, D., Fuchs, D., Arkhipkin, A.I., Hauff, R. B., Fritschi, B. and Klug, C. 2019. Predatory behaviour and taphonomy of a Jurassic belemnoid coleoid (Diplobelida, Cepahlopoda). Scientific Reports, 9: 7944, 11pp. [doi.org/10.1038/s41598-019-44260-w].

How to cite: Hart, M., Arratia, G., Moore, C., and Ciotti, B.: Life and Death in the Jurassic Seas of Dorset, Southern England, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1466, https://doi.org/10.5194/egusphere-egu2020-1466, 2020.

A key topic in paleoecology and macroevolution is whether assemblages of species show patterns of persistence over millions of years; a phenomenon that has been variously referred to as ‘Turnover Pulse’ or ‘Coordinated Stasis’. It has generally been presumed that any abrupt environmental changes discernible in the geological record will often lead to community turnover and the establishing of a new community that is discrete from the previous iteration, even if environmental conditions return to those that existed prior to the disruptive event. A related topic is, if patterns of stability can and do prevail despite disruption, what are the processes that allow for this. Potential options include the degree of change in the physical environment, which may not be great enough to exceed the threshold required for community collapse, or due to ‘Ecological Locking’, where directional selection is constrained by ecological processes.

Our touchstone to consider these topics is the detailed fossil record of Carboniferous brachiopod communities from the Mid-continent of North America. These were highly diverse communities that persisted in a very dynamic environmental setting. In particular, these communities were subjected to frequent and geologically rapid phases of marine transgression and regression associated with climate change over approximately a 20-million-year period. These changes likely resulted in repeated community destruction and renewal as suitable habitat was lost and then subsequently re-established.

Using a suite of statistical techniques, we characterized the nature and scope of changes in these fossil communities over time. We found that, at one scale, fossil communities were not stable throughout this interval, both in terms of taxonomic composition and the associated abundance of those taxa. Thus, there is no evidence of obdurate ecological stasis, as new discrete communities, statistically dissimilar from previous and subsequent iterations, form following each environmental disruption. However, at a higher scale, stability is manifest, as diversity patterns are stable across time and despite episodes of environmental change. In particular, we identify a form of qualified ecological stasis for both the different environments present during this interval and for the larger region as a whole. Ultimately, whilst the individual taxa that comprise each community differ, there is a consistent number of species that can exist in any given community, such that communities remain functionally similar. This indicates that whilst the individual taxa that come to form communities arrive via the exigencies of recruitment, the overall diversity of the communities is set by some higher-level ecological rules. Specifically, the rules for taxon packing are seemingly constant in distinct environments, likely due to energetic controls that limit how many taxa can be maintained in an environmental setting and/or perhaps because the amount of space needed for any individual to develop into an adult is invariant across different taxa within the same clade. Further, these ecological rules lead to stability even in the face of constant disequilibrium, which matches patterns identified in the recovery of marine invertebrate communities from disruptive events in modern systems.

How to cite: Strotz, L. and Lieberman, B.: Ecological stability despite environmental disruption – searching for ecological rules governing Carboniferous brachiopod assemblages from the North American Mid-continent, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2909, https://doi.org/10.5194/egusphere-egu2020-2909, 2020.

SSP1.2 – New and re-interpreted Pleistocene sea-level records from around the Globe

EGU2020-7153 | Displays | SSP1.2 | Highlight

Molecular fossils inferring Quaternary sea-level changes

Martina Conti, Martin Bates, Natasha Barlow, Richard Preece, Kirsty Penkman, and Brendan Keely

Targeted analysis of organic matter in soils and sediments is useful for evaluating past environmental conditions, as specific compounds may be directly linked to organisms and hence to the conditions in which they inhabited the environment.  Variations in molecular fossil distributions have become a powerful tool for understanding changes in palaeoclimate conditions.  This work uses molecular fossils to give an insight into the impact of transgressive events on primary producers inhabiting the studied basin, and hence a more detailed record of sea-level change.

The cores studied consisted of unconsolidated immature sediments from the mid-late Pleistocene (< 500,000 years) and the Holocene.  Molecular fossils, such as chlorophyll pigments and lipids, exhibit fluctuations as a response to changes in palaeoenvironmental conditions, providing a useful marker for sea-level changes.  Fluctuations in the pigment and n-alkane distribution reflect changes in primary producer activity, while the GDGT-based index of branched and isoprenoid tetraether lipids (BIT) differentiates between terrigenous and marine organic matter inputs.  Lipids were analysed by GC-FID and HPLC-MS while analysis of chlorophyll pigments was carried out using a new UHPLC-DAD method.

The results from biomarker analyses show excellent time-resolved agreement with previous lithological and ecological studies, but enabled a more sensitive response of different primary producers to changing conditions to be observed.  The molecular fossils were able to detect the onset and cessation of the studied transgressions earlier than it was possible with microfossil evidence.  Linking the pigment and lipid record with more secure dating will enable a more accurate record of Quaternary relative sea-level change.

How to cite: Conti, M., Bates, M., Barlow, N., Preece, R., Penkman, K., and Keely, B.: Molecular fossils inferring Quaternary sea-level changes, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7153, https://doi.org/10.5194/egusphere-egu2020-7153, 2020.

EGU2020-13660 | Displays | SSP1.2

The sea-level signal in Pleistocene shallow-marine records – examples from carbonate and siliciclastic sequences

Barbara Mauz, Zhixiong Shen, Natasha Barlow, David Hodgson, and Colin Woodroffe

It is generally accepted that sea-level change represents the most important boundary condition that controls stratigraphic architecture in the shallow-marine area and further downdip. The shallow-marine stratigraphic body is then a result of the changing ratio between sediment supply and accommodation space with a range of local (autogenic) processes interplaying with the eustatic (allogenic) sea level. Extracting the sea-level signal from this interplay is typically approached through rigorous interpretation of the indicative meaning of relevant sea-level markers and through comparison with the most appropriate glacio-isostatic adjustment (GIA) model. The latter comparison is insightful for the last glacial period, but for the Pleistocene it suffers from the dilemma that the GIA contribution to sea-level change cannot be predicted for a specific location unless the ice history is known but this is what the shallow-marine record is trying to reconstruct.

Here we aim for Pleistocene sea-level reconstructions that are largely independent of GIA predictions. For this we present Pleistocene shallow-marine records from high-, mid- and low-latitudinal settings. The presentation focuses on four aspects: type and quality of the data (e.g. outcrop, borehole, etc), preservation of the record, separation of allogenic versus autogenic signal and completeness of the eustatic cycle.

We show that in siliciclastic systems the preservation depends on sediment supply and on the coastal energy with which ravinement and regression surfaces obliterate the stratigraphic record. Separating autogenic from allogenic signals depends very much on data quality and the ability to reconstruct the antecedent topography. None of our records show a complete eustatic cycle from lowstand to highstand and back to lowstand where the missing part of the cycle seems to be indicative for the type of shallow-marine record and its location on earth.

We discuss reasons and implications of our findings and emphasise the need for far greater consideration of stratigraphic architecture, carbonate facies and facies correlation.

How to cite: Mauz, B., Shen, Z., Barlow, N., Hodgson, D., and Woodroffe, C.: The sea-level signal in Pleistocene shallow-marine records – examples from carbonate and siliciclastic sequences, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13660, https://doi.org/10.5194/egusphere-egu2020-13660, 2020.

EGU2020-17606 | Displays | SSP1.2

High resolution topography and modeling of the Huon coral reef terrace sequence (Papua New Guinea)

Gino de Gelder, Anne-Morwenn Pastier, Denovan Chauveau, David Fernández-Blanco, Kevin Pedoja, Christine Authemayou, and Laurent Husson

Coral reef terraces (CRT) are amongst the most important indicators of Quaternary sea level fluctuations, and are therefore relevant to a wide spectrum of climatic and tectonic studies. The Huon Peninsula in Papua New Guinea accomodates one of the first CRT sequences to be mapped, measured and dated in detail through pioneering studies several decades ago. Those studies were limited by the available techniques to assess the large scale terrace sequence morphology, and thus to constrain spatiotemporal uplift rate variations that are key to determine past relative sea-level (RSL). We re-visit the Huon CRTs with the aim of refining tectonic uplift rates and RSL, using digital surface models calculated from 0.5m Pleiades satellite imagery. This allows us to constrain variations in CRT elevation, and assess tectonic deformation wavelengths in detail. We then use a numerical code for coral reef modeling to reconstruct the sequence morphology and constrain the possible range of RSL over the past few glacial-interglacial cycles. We find that large-scale tilting of the terrace sequence is generally N- instead of NW-directed, which is more compatible with the regional tectonic setting. It also implies changes of several meters for RSL highstand estimates compared to previous studies. We compare our results to other terrace sequences, and discuss the potential of combining high-resolution topography with landscape evolution modeling to constrain RSL.

How to cite: de Gelder, G., Pastier, A.-M., Chauveau, D., Fernández-Blanco, D., Pedoja, K., Authemayou, C., and Husson, L.: High resolution topography and modeling of the Huon coral reef terrace sequence (Papua New Guinea), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17606, https://doi.org/10.5194/egusphere-egu2020-17606, 2020.

EGU2020-640 | Displays | SSP1.2

3D mapping of Quaternary coral reef terraces on Curacao Island, Southern Carribean Sea

Ciro Cerrone, Ann-Kathrin Petersen, Paolo Stocchi, Alessio Rovere, and Elisa Casella

Detailed geological field mapping is essential for the study of Relative Sea Level (RSL) indicators, that are in turn the only direct proxies to assess paleo sea level changes and long-term land movements. In the last decades, traditional mapping methods started to be complemented by small Remotely Piloted Aircraft Systems (RPAS, a.ka.a. drones) and high-resolution remote sensing datasets.

In this contribution, we show the results of geological mapping in the island of Curaçao (Netherlands Antilles). Here, we mapped a staircase sequence of coral reef terraces. In particular, we used TerraceM-2 Maptools (a Matlab® interface for mapping marine terraces) to extract wide-scale marine terrace elevations from TanDEM-X Digital Elevation Models (DEMs) (German Aerospace Center, DLR and Airbus). We detail the elevation information available for each single terrace with RPAS data processed with Agisoft Metashape, that allows obtaining as final products DEMs and orthophotos of selected sites at the inner margin of reef terraces. We then use land-based photogrammetry coupled with traditional facies analysis to identify geological discontinuities on the lower terrace.

The facies analysis allowed to precisely map the unconformity between the Hato (MIS 5.5) and Cortalein (MIS 7) Units (as identified by Muhs et al., 2012). The top of the Hato Unit forms the so-called “Curaçao Lower Terrace”. The top of the Hato Unit, extending few kilometres from the coast, has been mapped with both TanDEM-X and RPAS data up to the paleo-cliff of the Middle Terrace (formerly attributed to MIS 11), where a well-defined notch is preserved. We attribute this notch to the maximum sea ingression during MIS 5e. We compare its elevation with the RSL predicted by Glacio-Isostatic Adjustment (GIA) models.    

We discuss the new data and models for Curaçao in terms of long-term tectonic uplift and eustatic sea level.

Reference: Muhs DR, Pandolfi JM, Simmons KR, Schumann RR (2012) Sea-level history of past interglacial periods from uranium-series dating of corals, Curaçao, Leeward Antilles islands. Quat Res 78:157–169. doi: 10.1016/j.yqres.2012.05.008

Acknowledgments: TanDEM-X digital elevation data is used with permission within the Project DEM GEOL1210 (A. Rovere / M.E. Raymo). The fieldwork for this work was funded by the Helmholtz Exzellenznetzwerks “The Polar System and its Effects on the Ocean Floor (POSY)”. The authors acknowledge also the ZMT,  the Center for Tropical Marine Ecology, and the DAAD, the German Academic Exchange Service.

How to cite: Cerrone, C., Petersen, A.-K., Stocchi, P., Rovere, A., and Casella, E.: 3D mapping of Quaternary coral reef terraces on Curacao Island, Southern Carribean Sea, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-640, https://doi.org/10.5194/egusphere-egu2020-640, 2020.

As contribution to the ongoing research programmes RISeR (Dr. Barlow, Univ. Leeds, UK), WARMCOASTS (Dr. Rovere, Marum Bremen, GER) and LOSS (Dr. Stouthamer and consortium, Utrecht Univ., NL), and in more general effort to correctly deal with legacy geological data in the current era of Open Science and Geodata Science, we are populating the WARMCOASTS-WALIS database with entries for the Last-Interglacial sea-level indicator data points as available for the Southern North Sea area. This part of the world in in the immediate near field of the Scandinavian-British ice mass centre at interglacial temperate latitudes.

The majority of the sea-level indicator data points are of siliciclastic sedimentary type: transgressive contacts of marine muds over basal peats, insolation basin lakes becoming brackish marine, regressive peats establishing on tidal flat tops and so on. The abundance of peat and tradition of palynological investigation of these beds is important to date stratigraphical levels. The floating varve-count based PAZ-duration chronology for the Eemian vegetation succession in NW Europe (Zagwijn1996:QSR) allows to resolve floating ages to submillenial scale in the transgressive limb (PAZs E1-E4 and subzones), and to millennial scale in the high stand (coincident with PAZ E5) and regressive limb (starting at the PAZ E5/E6 break; Zagwijn1983:GeologieMijnbouw). Chronostratigraphical database entries for each zone and subzone have been filed in the WALIS database, informing on the varve count durations (floating time scale). Absolute age is left more broad, as there is some uncertainty and wiggle room and difference of opinion in the timing of the palynological NW European Eemian relative to that Termination II in the MIS and coral records (SierEtAl2015:QGeochron; LongEtAl2015:QSR).

Sedimentary environment analogies are drawn with the Holocene transgression and high stand to identify and classify localities as being sea-level indicator points (SLIPs), Marine limiting points, or Terrestrial limiting points. Analogies with the Holocene relative sea-level rise reconstruction practice (e.g. Hijma&Cohen2019:QSR) also echo in the protocols followed to characterize and document the vertical position of the indicator. Data entry requires to assess depth of contact (at present, expressed to a specified datum), implied depth position of past mean sea level (factoring in tidal range, palaeowater depth, background vertical movement, (de)compaction), and uncertainties to that depth (added up according to error propagation rules).

We compare our re-assessed and standardized database entries for longer established sites to the originally reported reconstructed sea-level positions (e.g. Zagwijn1983) and to their discussion in later publications (2000s, 2010s). What is one point in Zagwijn1983, often becomes an assemblage of terrestrial limiting, SLIPs and marine limiting entries in WALIS. We find the North Sea data in some earlier ‘table style’ global compilations to have suffered from generalisations. We find the protocolised database approaches as established by PALSEA activities (e.g. ShennanEtAl(Eds)2015: Handbook of Sea-Level Research; KahnEtAl(Eds)2019: QSR special issue) a more suitable environment to store and open up regional data for correct in-take and reuse by second/third parties - whether LOSS, WARMCOAST, RISeR, or you.

How to cite: Cohen, K.: Opening up a Last-Interglacial Sea Level Database for the Southern North Sea area, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3135, https://doi.org/10.5194/egusphere-egu2020-3135, 2020.

EGU2020-18309 | Displays | SSP1.2

Last Interglacial Sea-Level Indicators in the Western Indian Ocean

Patrick Boyden, Jennifer Weil Accardo, Pierre Deschamps, and Alessio Rovere

With global average temperatures 2°C higher than pre-industrial and eustatic sea-level ranging between 5 and 9 m above present, the Last Interglacial is often regarded as a good process-analogue for a future warmer climate.  Large uncertainties are associated with Last Interglacial eustatic sea-level estimations. To quantify these uncertainties through standardization of sea-level metadata, the World Atlas of Last Interglacial Shorelines (WALIS) provides a community-wide standard for documenting the geological context of sea-level indicators and their chronology. By applying this standard, WALIS allows for the quantitative cross-comparison between previous studies, often times separated by decades.

 

We use WALIS to review published sea-level indicators for the Last Interglacial within the Western Indian Ocean basin. Located in the far field with respect to past glaciations, the Western Indian Ocean has the potential to provide precisely measured and dated sea level proxies, enabling a reliable estimation of maximum eustatic sea level for the Last Interglacial. This, in turn, would allow to better constrain upper boundaries of melting within ice-sheet models. Furthermore, this review highlights localities that should be revisited based on the presence of geological facies indicative of former highstands where not enough detail has been reported or where advanced dating and geodetic techniques can increase the accuracy of metadata.

How to cite: Boyden, P., Weil Accardo, J., Deschamps, P., and Rovere, A.: Last Interglacial Sea-Level Indicators in the Western Indian Ocean, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18309, https://doi.org/10.5194/egusphere-egu2020-18309, 2020.

EGU2020-13281 | Displays | SSP1.2

Holocene sea-level changes in the Spermonde Archipelago, Indonesia: implications for vertical land movements

Alessio Rovere, Maren Bender, Thomas Mann, Paolo Stocchi, Dominik Kneer, Tilo Schöne, Julia Illigner, and Jamaluddin Jompa

We surveyed the elevation and age (14C) of paleo sea-level indicators in five islands of the Spermonde Archipelago. We describe 24 new sea-level index points from fossil microatolls, and we compare our dataset with both previously published proxies and sea-level predictions from a set of 54 Glacial Isostatic Adjustment (GIA) models, using different assumptions on both ice melting histories and mantle structure and viscosity. We then investigate the implications of our data and models in terms of vertical land movements in the study area, with two main results.

First, data from the heavily populated island of Barrang Lompo are significantly lower (ca. 80 cm) than those at all the other islands. In absence of instrumental data (e.g., GPS or tide gauges) in any of the islands, we advance the hypothesis that this difference may be due to groundwater extraction and loading of buildings on Barrang Lompo, that would cause this island to subside at rates in the order of ~3-11 mm/a.

Second, Common Era data (0-400 a BP) seem to indicate that the islands in the archipelago may be affected by tectonically-driven vertical land motions in the order of -0.88±0.61 mm/a (1-sigma), albeit slight uplift cannot be excluded. Different assumptions on vertical land motions affect, in turn, the assessment of which GIA model shows the best match with Late Holocene (ca. 4-5 ka) sea level data. Tectonic stability or slight uplift would favor iterations of ANICESELEN (De Boer et al., 2014), while subsidence would cause the sea level data to fit better with iterations of ICE-6G (Peltier et al., 2015).

References

De Boer, Bas, Paolo Stocchi, and Roderik Van De Wal. A fully coupled 3-D ice-sheet-sea-level model: algorithm and applications." Geoscientific Model Development 7.5 (2014): 2141-2156.

Peltier, W. R., D. F. Argus, and R. Drummond. Space geodesy constrains ice age terminal deglaciation: The global ICE‐6G_C (VM5a) model. Journal of Geophysical Research: Solid Earth 120.1 (2015): 450-487.

Acknowledgments

This project is funded by SEASCHANGE (RO-5245/1-1) and HAnsea (MA-6967/2-1) from the Deutsche Forschungsgemeinschaft (DFG), part of the Special Priority Program (SPP)-1889 "Regional Sea Level Change and Society". Parts of this study are under review in Climate of the Past (https://www.clim-past-discuss.net/cp-2019-63/)

How to cite: Rovere, A., Bender, M., Mann, T., Stocchi, P., Kneer, D., Schöne, T., Illigner, J., and Jompa, J.: Holocene sea-level changes in the Spermonde Archipelago, Indonesia: implications for vertical land movements, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13281, https://doi.org/10.5194/egusphere-egu2020-13281, 2020.

EGU2020-12416 | Displays | SSP1.2

Driving mechanisms of sea-level variability in the U.S. mid-Atlantic during the last millennium

Jennifer Walker, Robert Kopp, Nicole Khan, Timothy Shaw, Niamh Cahill, Don Barber, Matt Brain, Jennifer Clear, Reide Corbett, and Benjamin Horton

Last millennium relative sea-level (RSL) changes along the U.S. Atlantic coast are spatially variable. Glacial isostatic adjustment (GIA) has been a significant driving factor in RSL rise during the last millennium, producing maximum rates of vertical land motion in the mid-Atlantic region due to its proximity to the margin of the former Laurentide Ice Sheet. However, there is uncertainty surrounding the influence of other regional and local processes on RSL changes such as ocean and atmosphere circulation dynamics; gravitational, rotational, and deformational signals associated with ice mass and distribution changes; sediment compaction; and tidal range change.

Here, we examined the high spatial density of high-resolution RSL records along a ~200 km stretch of coastline from New York City to southern New Jersey to distinguish between local, regional, and global scale drivers. We produced a new high-resolution (decimeter vertical, decadal temporal) RSL record of the last millennium in northern New Jersey and integrated it into an updated global database of instrumental and proxy sea-level records of the Common Era. We used a spatiotemporal empirical hierarchical model to estimate past RSL and rates of RSL change and their associated uncertainties in the context of broader regional changes by decomposing the records into global, regional linear, regional non-linear, and local components.

We found that RSL in northern New Jersey continuously rose over the last 1000 years at a rate of 1.2 ± 0.2 mm/yr (2σ) from 1000 to 1700 CE before increasing to 1.3 ± 0.7 mm/yr from 1700-1800 CE to 1.8 ± 0.6 mm/yr from 1800-1900 CE to 3.0 ± 0.6 mm/yr from 1900-2000 CE. Most of the RSL rise during the past 1000 years is attributed to regional-scale linear processes that we interpret primarily as GIA. The linear component of the RSL records exhibits a north to south gradient, with a greater contribution of RSL rise in southern New Jersey and a smaller contribution in New York City. The regional-scale non-linear contribution from the records have a magnitude <10 cm and are nearly identical because they fall within the same regional scale determined by the spatiotemporal model. The rate of the regional non-linear component fluctuated between -0.1 and 0.1 mm/yr until the late 19th century when it increased to a rate of 0.6 ± 0.1 mm/yr in the late 20th century. These trends are likely explained by a combination of physical processes, including the evolving mass of the Greenland Ice Sheet, steric effects, or ocean mass changes from atmospheric circulation and ocean currents. The local-scale contribution is <10 cm at all sites, but varies in magnitudes and rates of change, which may be due to sediment compaction or tidal range change.

How to cite: Walker, J., Kopp, R., Khan, N., Shaw, T., Cahill, N., Barber, D., Brain, M., Clear, J., Corbett, R., and Horton, B.: Driving mechanisms of sea-level variability in the U.S. mid-Atlantic during the last millennium, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12416, https://doi.org/10.5194/egusphere-egu2020-12416, 2020.

EGU2020-1678 | Displays | SSP1.2

Relative sea level highstands of the Yucatán Peninsula, Mexico, constrained by speleothem growth periods

Simon Dominik Steidle, Sophie Warken, Norbert Frank, Julius Förstel, Nils Schorndorf, Andrea Schröder-Ritzrau, Gina Moseley, Wolfgang Stinnesbeck, and Jerónimo Avilés Olguín

The loading of the North American continent with ice sheets causes a geomorphologic response. As a result of this process, a NW-SE gradient of relative sea level developed in the Caribbean during periods of glaciation. In order to distinguish geomorphologic and eustatic contributions it is important to resolve timing and amplitude of relative sea level at different positions in the Caribbean.

The cave systems around Tulum, Quintana Roo, Mexico are presently submerged and well-connected to the nearby Atlantic with a low hydraulic head gradient. Speleothems must have formed during periods of lower sea level, thus providing constraints on the maximum elevation of relative sea level for given periods of time. Conversely, periods of growth cessation could have been caused by sea level rise thus indicating minimum relative sea level during highstands.

Here, we present 230Th/U dated submerged speleothems that grew during MIS5a-d as well as MIS1/2, MIS6 and MIS11/12.

Growth of a single stalagmite (QUE01) at -10.8±0.1m (relative to today's sea level) was interrupted twice. Petrographical studies and trace element analysis indicate that submergence caused millennial-scale growth stops in QUE01 during MIS5. The proposed highstands are between 109.4±0.3ka and 105.0±0.3ka as well as between 104.5±0.4ka and 96.9±0.4ka.

While a previous study [1] constrains the amplitude to <9.9m, this study further improves the timing. This is the first record in this area that yields bracketing ages for those highstands from a speleothem that is very close to the peak height. In order to reconstruct a Caribbean sea level gradient, the combined Yucatán record acts as a counterpiece to a similar study from the northern end of the Caribbean sea level gradient which reports highstands at that time with a higher relative sea level [4].

Speleothem growth during MIS1/2 (19-8ka) relates to conflicting local sea level markers [2,3] and contains century-scale growth stops. Samples dating back to MIS6 and MIS11/12 highlight the potential for sea level reconstruction in this area before MIS5.

[1] Moseley et al. (2013) Journal of Quaternary Science 28 293-300
[2] Moseley et al. (2015) The Holocene 25 1511-1521
[3] Hering et al. (2018) Journal of Quaternary Science 33 444-454
[4] Wainer et al. (2017) Earth and Planetary Science Letters 457 325-334

How to cite: Steidle, S. D., Warken, S., Frank, N., Förstel, J., Schorndorf, N., Schröder-Ritzrau, A., Moseley, G., Stinnesbeck, W., and Olguín, J. A.: Relative sea level highstands of the Yucatán Peninsula, Mexico, constrained by speleothem growth periods, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1678, https://doi.org/10.5194/egusphere-egu2020-1678, 2020.

EGU2020-18523 | Displays | SSP1.2

Pleistocene sea-level record in low latitude settings: the Cape Verde Islands.

Teresa Bardají, José Luis Goy, Caridad Zazo, Claude Hillaire-Marcel, Cristino J. Dabrio, Ángel Gozález, Bassam Ghaleb, Ana Cabero, Vicente Soler, and Javier Lario

The volcanic Cape Verde archipelago constitutes one of the few sites in low latitude eastern Atlantic Ocean, where a long record of Pleistocene sea-level indicators develops, particularly beach deposits and marine terraces. The extreme aridity of the easternmost islands (Sal, Boa Vista and Maio) allows the exposure of long sedimentary sequences, the altitudinal and spatial distribution of which must be related both to sea level behaviour in low latitude settings and also to the volcanic nature of the archipelago.

The particular case of Maio Island reveals the occurrence of a flight of at least 18 marine terraces, between +85 and 0m. The chronology has been approached by a paleomagnetic sequence (Early - Middle Pleistocene transition), U-series measurements (Last Interglacial deposits) and 14C (Holocene units).

The results have revealed a differential behaviour in the vertical motion of the island along the Pleistocene, with unequal uplift rates during Early and Middle Pleistocene. An anomalously low-lying MIS5 unit in this island fits well with the predictions done by GIA models of Crevelling et al., (2017) although the proper evolution of volcanic islands cannot be discarded.

A comparison with Sal (Zazo et al., 2007, 2010) and Boa Vista islands is done, especially in what the MIS5 sea level record is concerned. MIS 5e deposits are scarce along the coasts of Maio and Boa Vista, and always at very low heights above mean sea level (0-0,5 m). On the island of Sal the deposits corresponding to the MIS 5e are located at a maximum height of +2.5m asml, in its most southern sector, being also very frequent to find them at 0m (Zazo et al., 2010).

The geomorphological distribution of the Pleistocene sedimentary sequences along these three islands reveals a complex history of uplift and subsidence that must be conciliated with the far-field sea level behavior, especially for the MIS5 units.

Creveling et al., 2017. QSR 163.

Zazo et al., 2007. QSR 26.

Zazo et al., 2010. GPCh 72.

Acknowledgements: This work has been supported by FEDER-MINECO Spanish project CGL15-69919-R.

How to cite: Bardají, T., Goy, J. L., Zazo, C., Hillaire-Marcel, C., Dabrio, C. J., Gozález, Á., Ghaleb, B., Cabero, A., Soler, V., and Lario, J.: Pleistocene sea-level record in low latitude settings: the Cape Verde Islands., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18523, https://doi.org/10.5194/egusphere-egu2020-18523, 2020.

EGU2020-10423 | Displays | SSP1.2

Last Interglacial fossiliferous sequences from Santiago Island (Cabo Verde Archipelago): the palaeoecology of the Nossa Senhora da Luz section, a rare example of a protected bay in volcanic oceanic islands

Carlos Melo, José Madeira, Ricardo S. Ramalho, Ana C. Rebelo, Michael Rasser, Esther González, Alfred Uchman, Patrícia Madeira, Emílio Rolán, Luís Silva, Carlos M. da Silva, Deirdre Ryan, Alessio Rovere, Mário Cachão, and Sérgio P. Ávila

The world-wide study of the geological record of the Last Interglacial is key to reconstruct the climatic and oceanographic conditions during that time interval. Here we present preliminary results of a comprehensive field analysis of one of the most extensive and least studied Quaternary fossiliferous sequences in Cabo Verde attributed to the Last Interglacial. It is located at Nossa Senhora da Luz, which is a protected inlet at the SE coast of Santiago Island. The studied sequence shows a set of transitions between fluvial and marine environments, and emersion and immersion events within a confined, highly protected bay environment. The presence, in the upper part of the sequence, of a thick layer of very fine-branched rhodoliths indicates particular ecological conditions within this bay (e.g., shallow and turbidity free waters, stable environmental conditions and/or fast growth) that are absent today and presumably played an important role for the presence of particular invertebrate species during that time. The presence of tidal specimens of the clam Senilia senilis in life position at an altitude of ~12m above sea-level allowed a re-interpretation of relative sea-level changes, suggesting that the uplift trend of Santiago Island for the Last Interglacial period onwards (3m/100ky) is possibly 70% lower than previously calculated (10m/100ky). Fossils include five phyla, with molluscs being the most diverse and abundant. Despite the abundance of some species (e.g., the bivalves Saccostrea cuccullata, S. senilis, and Aequipecten opercularis, and the gastropods Persististrombus latus and Thais nodosa), the general biodiversity is low. The presence of S. cuccullata and S. senilis, absent from extant Cabo Verdean faunas, indicates a more humid climate, unlike the dry climate found today. Some horizons are intensively bioturbated with the crustacean burrow Thalassinoides suevicus. Our new data agree with the hypothesised palaeoclimatic framework of more wet conditions than today for the Last Interglacial in the archipelago.

Keywords: Eemian, Cabo Verde Archipelago, sheltered bay, Senilia senilis, volcanic oceanic islands, NE Atlantic

Acknowledgments

C.S.M. and A.C.R. acknowledge, respectively, his PhD grant M3.1.a/F/100/2015 from FRCT/Açores 2020 and her Post-Doc grant SFRH/BPD/117810/2016 by FCT. R.R. and S.Á. acknowledges his IF/01641/2015 and IF/ 00465/2015 grants funded by FCT. A.R. and M.R. were supported by the by DFG grant RA1597/3-1. This work was supported by FCT project PTDC/CTA-GEO/28588/2017 and LISBOA-01-0145-FEDER-028588 UNTIeD and DRCT 2019-2022 – ACORES-01-0145_FEDER-000078 – VRPROTO.

How to cite: Melo, C., Madeira, J., Ramalho, R. S., Rebelo, A. C., Rasser, M., González, E., Uchman, A., Madeira, P., Rolán, E., Silva, L., Silva, C. M. D., Ryan, D., Rovere, A., Cachão, M., and Ávila, S. P.: Last Interglacial fossiliferous sequences from Santiago Island (Cabo Verde Archipelago): the palaeoecology of the Nossa Senhora da Luz section, a rare example of a protected bay in volcanic oceanic islands, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10423, https://doi.org/10.5194/egusphere-egu2020-10423, 2020.

EGU2020-14805 | Displays | SSP1.2 | Highlight

The southern North Sea as a natural palaeo-laboratory to reconstruct the coastal response to Last Interglacial sea-level rise

Natasha Barlow, Victor Cartelle, Oliver Pollard, Lauren Gregoire, Natalya Gomez, David Hodgson, Stephen Eaton, Freek Busschers, Kim Cohen, Carol Cotterill, Claire Mellett, and Ivan Haigh

Current models that project sea-level rise beyond 2100 have large uncertainties because recent observation encompass a too limited range of climate variability to provide robust tests against which to simulate future changes. It is crucial to turn to the geological record where there are large-scale changes in climate, but the current interglacial provides limited evidence for how the Earth-system responds to increased temperatures, and therefore it is necessary to study previous climatically-warm periods. Global temperatures during the Last Interglacial were ~1oC warmer than pre-industrial values and 3-5oC warmer at polar latitudes, during which time global mean sea level was likely 6-9 m above present. Though the drivers of warming during the Last Interglacial are different to those of today, it is the amplified warming at polar latitudes, the primary locations of the terrestrial ice masses likely to contribute to long term sea-level rise, which makes the Last Interglacial an ideal palaeo-laboratory to understand coastal response to sea-level rise.  However, our understanding of Last Interglacial sea level change is primarily limited to tropical and sub-tropical latitudes and it is important to understand the response of temperate estuarine settings to rising sea level.

The ERC-funded RISeR project (Rates of Interglacial Sea-level Change, and Responses) focuses on specifically targeting palaeo shorelines buried within the southern North Sea, preserved beyond the limit of the Last Glacial Maximum ice sheets. Buried Last Interglacial sequences in this area provide a valuable record of marine transgression and are being unveiled in new geophysical and geotechnical datasets acquired to support the offshore renewable energy development. This offshore sedimentary archives offer significant advantages over the geomorphologically restricted onshore records allowing us to trace the transgression over a much large area, and should capture the earliest flooding of the Last Interglacial North Sea basin, when the far-field data suggests ice sheet melt was at it maximum. By integrating the already available datasets with newly acquired samples as part of the project, we aim to develop new palaeoenvironmental reconstructions of the Last Interglacial sea-level change from northwest Europe, providing the first chronological constraints on timing, and therefore rates. This has the potential to allow us to ‘fingerprint’ the source of melt (Greenland and/or Antarctica) during the interglacial sea-level highstand.

How to cite: Barlow, N., Cartelle, V., Pollard, O., Gregoire, L., Gomez, N., Hodgson, D., Eaton, S., Busschers, F., Cohen, K., Cotterill, C., Mellett, C., and Haigh, I.: The southern North Sea as a natural palaeo-laboratory to reconstruct the coastal response to Last Interglacial sea-level rise, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-14805, https://doi.org/10.5194/egusphere-egu2020-14805, 2020.

EGU2020-4450 | Displays | SSP1.2

Late Pleistocene – Holocene sea level and climate changes in the Black Sea

Andrei Briceag, Gabriel Ion, Mihaela Melinte-Dobrinescu, Dan Vasiliu, and Naliana Lupascu

The Danube Deep-Sea Fan, situated in NW Black Sea, is one of the most developed deep-sea sedimentary structures in Europe (Panin & Jipa, 2002). In 2018, in the framework of the uBiogas Project (24PCCDI/2018), several cores were acquired from the aforementioned area. In this study, high resolution microfaunal analyses coupled with sedimentological and geochemical ones, were performed on two gravity cores that revealed changes since the Last Glacial Maximum. The cores have been collected from two secondary canyons, situated in the E of the Danube Canyon, at 655,7 m (MN183_3_GC_1) and 1315 m water depths (MN183_8_GC_1). In both cores, three stratigraphic units as described by Ross & Degens (1974) were identified (oldest first): Unit 3 (Lacustrine lutite), Unit 2 (Sapropel Mud) and Unit 1 (Coccolith Mud).

The sediments of Unit 3 correspond to the Last Glacial Maximum and are marked by the presence of the cold-water ostracod species. The cores contain a reddish-brown clay and silty interval belonging to the post-glacial melt-water pulse of the Heinrich Event 1. In these deposits the ostracod assemblages display a high diversity and abundance. The CaCO3 amount is very low, i.e. below 15%, except for the upper part where it reaches more than 50%. The samples of Unit 3 contain nannofossil assemblages that are entirely composed of reworked species from Cretaceous, Paleogene, Early and Middle Miocene intervals.

In Unit 2 (the sapropel), very few specimens of ostracods were identified, towards the top. During this depositional interval CaCO3 values are dropping again below 15%. The high abundance of the calcareous nannoplankton species Braarudosphaera bigelowii in the upper part of Unit 2 suggests the first strong influx of marine waters into the Black Sea basin.

In the youngest Unit 1, a brackish-marine ostracod assemblage, with low diversity and abundance was identified. This interval is characterized by the presence of polyhaline ostracods with Mediterranean origin. The ostracods from this assemblage tolerate salinities comprised between 17-21 ‰ and characterize a sub-littoral environment. The CaCO3 values are increasing to more than 50%. During the depositional interval of Unit 1 the environmental was definitely a marine one, probably with a constant salinity of surface waters over 17 ppm, allowing the calcareous nannoplankton species Emiliania huxleyi and Braarudosphaera bigelowii to proliferate. The great abundance of the two taxa and especially of Emiliania huxleyi indicates the existence in the basin of a high nutrient input.

The financial support for this paper was provided by the Romanian Ministry of Research and Innovation, through the Programme 1 – Development of the National System of Research – Institutional Performance, Project of Excellence in Research-Innovation, Contract No. 8PFE/2018 and by the Project uBiogas, contract no. 24PCCDI/ 2018.

 

Panin, N., Jipa, D., 2002. Danube river sediment input and its interaction with the northwestern Black Sea. Estuarine Coastline Shelf Science 54: 551–562.

Ross, D.A., Degens, E.T., 1974. Recent sediments of the Black Sea. In: Degens E.T. and Ross D.A. (Eds.), The Black Sea: Geology, Chemistry, and Biology. American Association of Petroleum Geologists, Tulsa, USA: 183–199.

How to cite: Briceag, A., Ion, G., Melinte-Dobrinescu, M., Vasiliu, D., and Lupascu, N.: Late Pleistocene – Holocene sea level and climate changes in the Black Sea, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4450, https://doi.org/10.5194/egusphere-egu2020-4450, 2020.

SSP1.3 – Earth System Paleobiology: closing the geological and biological gap

EGU2020-832 | Displays | SSP1.3 | Highlight

Morphology in time and space: how does shape change with sequence stratigraphic architecture?

Judith Sclafani, Max Christie, Marjean Cone, Brooke Roselle, Audrey Bourne, Caroline Gazze, and Monika O'Brien

In their seminal work on stratigraphic paleobiology, Patzkowsky and Holland highlighted the need for more morphological data that are placed within a stratigraphic context in order to more robustly study the impact of environmental change on morphological disparity. The ability to collect morphological data within sequence stratigraphic architecture has been limited by technique. As a result, most morphological data are collected from museum specimens, usually without sequence stratigraphic information. We used the photogrammetry technique, Structure-from-Motion, to collect brachiopod morphological data from outcrops in the Late Ordovician Cincinnati Arch (Indiana, Ohio, Kentucky; USA) and quantify morphological change within an established sequence stratigraphic architecture.

SfM uses 2D photographs taken from different angles to reconstruct a 3D shape. We photographed external valves of brachiopods in the field in 360 degrees (approximately 24 photos per specimen) and used the SfM software ‘Agisoft Metashape’ to make 3D models of those specimens. We exported these models into R and used the package ‘geomorph’ to generate a set of semi-landmarks. We used these to create a morphospace to explore the effects of environment and time on 3D shape.

Results indicate that brachiopod shells separate in morphospace according to their degree of inflation and roundness. These differences are likely controlled by environmental conditions at each position along a water depth gradient. Additionally, our results are consistent with the previously observed breakdown of the environmental gradient in response to the Richmondian invasion. In particular, for the genera Rafinesquina and Cincinitina, pre-invasion specimens inhabit a larger proportion of morphospace, with more specimens exhibiting an ovular outline. Post-invasion specimens contract in morphospace, exhibiting a more rectangular shape. However, Cincinitina is missing from the offshore environment in the C2 sequence and the deep subtidal environment in the C5 sequence, making it difficult to distinguish the effects of invasion from ecophenotypic variation.

Ultimately, our study demonstrates that SfM makes gathering 3D morphological data from the field possible. Because this is a low-cost and easily accessible method, possibilities of applying it more broadly within paleobiology abound. Further development of this technique will not only provide a better understanding of the distribution of morphological form within stratigraphic architecture, but also increase the quantity of morphological data from key intervals throughout the Phanerozoic. These data can be stored as a digital archive that could facilitate large-scale meta-analyses as well as education and outreach activities.

How to cite: Sclafani, J., Christie, M., Cone, M., Roselle, B., Bourne, A., Gazze, C., and O'Brien, M.: Morphology in time and space: how does shape change with sequence stratigraphic architecture?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-832, https://doi.org/10.5194/egusphere-egu2020-832, 2020.

EGU2020-126 | Displays | SSP1.3 | Highlight

Estimating Downcore Decline in Skeletal Disintegration Risk in Holocene Environments

Niklas Hohmann and Adam Tomašových

Preservation of skeletal remains is thought to be positively linked to rate of burial, i.e., they are exposed to destructive processes for a shorter time under higher burial. However, downcore changes in time-averaging documented in Holocene skeletal assemblages implies that per-individual burial rates of skeletal remains of the same age cohort can be variable, e.g., owing to bioturbation, and estimation of time (and sediment depth) over which skeletal remains are exposed to destruction is not straightforward.

This variability in the depth of burial exposes them to different intensities of destructive processes that is typically highest in sediments on or close to the seafloor, and accordingly changes their probability of disintegration. This hinders both the reconstruction of taphonomic conditions downcore and the reconstruction of biological archives from age cohorts of skeletal remains.

We present the AALPS (Aging ALong burial PathS) model to estimate downcore disintegration risk and taphonomic age, based on sediment-depth distribution of postmortem age of individual skeletal remains. This model can be applied to individual cores and taxa, accounts for sediment mixing and time-averaging, and incorporates knowledge of changing sediment input.

As an application, we discriminate between distinct hypotheses of changes in skeletal disintegration rates in cores from the Adriatic Sea.

The method provides new insights into the taphonomy of skeletal remains in Holocene and Anthropocene environments and age unmixing of paleoecological time series, which can be used in conservation paleobiology to reconstruct ecological baselines to guide future conservation efforts.

How to cite: Hohmann, N. and Tomašových, A.: Estimating Downcore Decline in Skeletal Disintegration Risk in Holocene Environments, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-126, https://doi.org/10.5194/egusphere-egu2020-126, 2020.

EGU2020-1049 | Displays | SSP1.3

Reconstruction of the trophic levels of a fossil fish community from the Late Jurassic Solnhofen Archipelago

Danijela Dimitrijevic, Martin Ebert, Martina Kölbl-Ebert, and Axel Munnecke

Trophic interactions of extinct fishes are central to our understanding of evolution, paleoecology and their role in the paleo-communities, but can be challenging, as these are limited by the incompleteness of the fossil record and by a lack of behavioural data. The extensive fossil record of Actinopterygii comes mostly from Conservation-Lagerstätten. They provide exceptionally rich information on fossil ecosystems and open outstanding windows into the evolution of life. The best-preserved Late Jurassic actinopterygians are known from the Solnhofen Archipelago, Germany. Despite that the diversity ichthyofauna of the Solnhofen Archipelago has been extensively explored in the last several decades, the dietary preferences of most fish remain unknown or have to be deduced by analogy from dentition and jaw morphology.

The aim of this study was to reconstruct the trophic levels of Late Jurassic fish assemblages using Sr/Ca and Ba/Ca measured from phosphatic fish remains, mostly ganoin and cycloid scales recovered from the Ettling locality, which is characterized by exceptionally well-preserved fossil fishes and moderate diagenetic alteration. We classified fish species into four trophic levels (durophagous, lower, middle, and higher trophic level) based on morphology available from the literature. Mean values of Sr, Ca, Ba and their ratios measured by Thermo Scientific iCAP Q inductively coupled plasma mass spectrometer in this study are in accordance with the mean values of previous studies. Differences in values between cleaned and uncleaned samples showed that the cleaning process successfully isolated primary dietary Sr content while dissolving away the diagenetic strontium present in carbonate in the pore spaces. All trophic levels showed low variation of Sr/Ca (0.003 - 0.008 μg/g) and high variation of Ba/Ca values (0.0003 - 0.0014 μg/g). The results showed significant differences between the middle and higher trophic levels (p = 0.03), while durophagous and lower trophic levels fell into the same range of values as the higher trophic level. 

We demonstrate that enamel of fossil vertebrates from the Solnhofen Archipelago still contains near-in vivo Sr, Ba, and Ca. The clear distinction between middle and higher trophic levels offers a new functional perspective on the ecological and evolutionary relationships among fishes. However, future studies should not neglect the importance of diagenetic alteration of the samples; proper sample cleaning before measuring isotopic signatures, and careful selection of the analyzed tissue (i.e. tooth enamel instead of scales or bones due to its resistance to diagenesis).

How to cite: Dimitrijevic, D., Ebert, M., Kölbl-Ebert, M., and Munnecke, A.: Reconstruction of the trophic levels of a fossil fish community from the Late Jurassic Solnhofen Archipelago , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1049, https://doi.org/10.5194/egusphere-egu2020-1049, 2020.

EGU2020-3456 | Displays | SSP1.3

Cenozoic plankton diversity dynamics and the impact of macroevolution on the marine carbon cycle.

Johan Renaudie, David Lazarus, Sarah Trubovitz, Volkan Özen, Gabrielle Rodrigues de Faria, Gayane Asatryan, and Paula Noble

The marine biological carbon pump is one of the most important mechanism to extract carbon from the atmosphere and export it to the deep-sea and the sediments, and thus take it out from the cycle for millions of years. Today, marine planktonic diatoms are the main element of that pump; however at the beginning of the Cenozoic they were too rare and not diverse enough to have much geochemical significance. Calcareous nannofossils and foraminifera on the other hand were already important components of the carbonate carbon pump; however they also contribute to the alkalinity pump which on shorter timescales have an adverse effect on carbon sequestration. In addition, heterotrophic, amoeboid protists, in particular polycystine radiolarians, are also known to contribute significantly to the carbon export to the deep-sea due to their role in forming rapidly sinking particles of aggregated organic material. We present new diversity reconstructions using the Neptune database (NSB) and case studies focussed on the Late Neogene and the Eocene-Oligocene transition using newly collected full-fauna/flora diversity data. We will then show how the diversity and abundance history of these groups changed throughout the Cenozoic, what the role of climate/oceanographic changes and competition on their evolution was, and, in the end, what consequences their evolution had on the marine carbon cycle.

How to cite: Renaudie, J., Lazarus, D., Trubovitz, S., Özen, V., Rodrigues de Faria, G., Asatryan, G., and Noble, P.: Cenozoic plankton diversity dynamics and the impact of macroevolution on the marine carbon cycle., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3456, https://doi.org/10.5194/egusphere-egu2020-3456, 2020.

EGU2020-5799 | Displays | SSP1.3 | Highlight

The impact of the Messinian Salinity Crisis on marine biota

Konstantina Agiadi, Niklas Hohmann, Giorgio Carnevale, Elsa Gliozzi, Constanza Faranda, Francesca Lozar, Mathias Harzhauser, George Iliopoulos, Antonio Caruso, George Kontakiotis, Marco Taviani, Alan Maria Mancini, Enrico Borghi, Ildefonso Bajo Campos, Pierre Moissette, Danae Thivaiou, Stergios Zarkogiannis, Eva Besiou, Daniel Garcia-Castellanos, and Angelo Camerlenghi

The Messinian Salinity Crisis (MSC) was the greatest paleoenvironmental perturbation the Mediterranean has ever seen. The literature is abundant in hypotheses on the repercussions of the MSC on organisms. However, all these are based on incomplete and still uncertain scenarios about the MSC evolution, as well as on the assumption that such a paleoenvironmental perturbation must have completely reset marine biota. Having prevailed for many decades now, this assumption has leaked from paleontology and geosciences to biological sciences, with numerous studies taking this scenario for granted instead of using it as a starting hypothesis to be tested. Here, we review and revise the marine fossil record across the Mediterranean from the Tortonian until the Zanclean to follow the current rules of nomenclature, correct misidentifications, and control for stratigraphic misplacements. We examine the composition of marine faunas, both taxonomically and considering the function of each group in the marine ecosystem and the transfer of energy through the marine food web. Specifically, we investigate the following functional groups: 1) primary producers, 2) secondary producers, 3) primary consumers, 4) secondary consumers, and 5) top predators. Our study includes sea grasses, phytoplankton, corals, benthic and planktonic foraminifera, bivalves, gastropods, brachiopods, echinoids, bryozoans, fishes, ostracods, and marine mammals. We calculate biodiversity indexes to provide independent evidence quantifying to what degree the marine fauna underwent:

How to cite: Agiadi, K., Hohmann, N., Carnevale, G., Gliozzi, E., Faranda, C., Lozar, F., Harzhauser, M., Iliopoulos, G., Caruso, A., Kontakiotis, G., Taviani, M., Mancini, A. M., Borghi, E., Bajo Campos, I., Moissette, P., Thivaiou, D., Zarkogiannis, S., Besiou, E., Garcia-Castellanos, D., and Camerlenghi, A.: The impact of the Messinian Salinity Crisis on marine biota, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5799, https://doi.org/10.5194/egusphere-egu2020-5799, 2020.

Although the temporal resolution and incompleteness of the fossil record are strongly determined by the thickness of the taphonomic active zone and by the depth and rate of mixing, it is unclear whether changes in time-averaging associated with the burial of assemblages that form in the surface mixed layer (SML) can be generalized across environments. Here we extend our previous models, which estimated disintegration on the basis of shell-age distributions (AFDs) in the SML, to stochastic transition matrices, and then apply them to discrete stratigraphic layers in sediment cores. This permits us to: (1) predict downcore trends in the shape of shell AFDs, and (2) estimate burial, disintegration, and mixing rates on the basis of age distributions observed in sediment cores. We find that, first, if the time to burial of individual shells to a specific sediment depth is stochastic due to bioturbation, then the inter-quartile age range will increase and skewness and kurtosis will decrease downcore to the top of permanent, historical layers (because the deepest layers reached by bioturbators are affected by mixing for a longer time than are surface layers). Systematic dm- to meter-scale changes in AFDs downcore can thus arise without changes in rates of sedimentation or mixing. Second, in contrast to expectations that species with durable shells will exhibit greater time averaging (larger inter-quartile age ranges) than species with fragile shells (an effect typical of assemblages in the SML), this difference will be minimized below the taphonomically active zone. Third, the median and modes of the AFDs of species differing in durability will differ, however, in those subsurface assemblages, producing age offsets (geologic age discordance) among species. These three predictions are clearly relevant for Holocene-Anthropocene studies, but also inform our understanding of deeper time fossil records, where episodically rapid burial can move surface assemblage to historical layers. In such case, the downcore decline in time averaging associated predicted by the surface-subsurface transition will characterize some subsets of stratigraphic successions in the fossil record.

How to cite: Tomašových, A., Kidwell, S. M., and Dai, R.: Modeling the transition of death assemblages from surface to subsurface: predicting the effects of burial, mixing, and disintegration on time averaging, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7099, https://doi.org/10.5194/egusphere-egu2020-7099, 2020.

Environmental gradients are among the primary drivers of change in ecological communities through time and space. However, what is rare are combined data sets of community composition and the environmental factors that may have caused ecological turnover, largely because many environmental variables are difficult to measure in the stratigraphic record. In this study we integrate quantitative abundance estimates of benthic macroinvertebrates with a multivariate dataset of geochemical proxies to potentially estimate the environmental drivers of faunal change through the 13 m.y. history of the Middle–Late Jurassic Sundance Seaway, western United States.

Faunal counts of macroinvertebrates were obtained from marine rocks of the Gypsum Spring, Sundance and Twin Creek formations at 19 localities in Wyoming, Montana and South Dakota. From the same localities, calcitic shells of selected species (Gryphaea planoconvexa, Gryphaea nebrascensis, Gryphaea sp., Liostrea strigilecula, Deltoideum sp.), were analysed for stable isotope (carbon and oxygen) and elemental (Mg/Ca, Sr/Ca, Na/Ca, Ba/Ca) geochemistry. The studied interval was subdivided into seven third-order depositional sequences representing carbonate ramp, wave-dominated, siliciclastic shelf, siliciclastic tidal coast, and mixed evaporite-siliciclastic desert systems. Of these, five depositional sequences were fossiliferous.

Ordination plots (nMDS) of the two palaeoecological and geochemical datasets are very similar (procrustes correlation: 0.75, p: 0.0001). Vector fitting of geochemical data on the palaeoecological ordination shows that a main faunal turnover event, corresponding to the shift from carbonate to siliciclastic deposition at the Middle–Late Jurassic transition, correlates with an increase in productivity (increase of δ13C) and a decrease in temperature (decrease of Mg/Ca ratio) through time. Position of fauna in the seaway (craton vs. foredeep) correlates instead with variations of δ18O and Ba/Ca ratio, suggesting a strong salinity gradient, with decreasing salinity moving from the craton towards the foredeep. A critical discussion of these results will also include factors that could potentially affect temporal changes of proxy data, such as species-specific vital effects.

How to cite: Danise, S., Holland, S., and Price, G.: Combining palaeontological and geochemical data to reconstruct environmental gradients, a case study from the Jurassic Sundance Seaway, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9795, https://doi.org/10.5194/egusphere-egu2020-9795, 2020.

Despite much scientific effort aimed over the past three decades to better constrain the fossil record of chemosynthesis-based communities, our understanding of their early evolution remains fragmentary. Until recently, a dominant perception was that, unlike the Cenozoic, bivalve-dominated chemosynthetic ecosystems, the Paleozoic to mid-Mesozoic methane seeps and hydrothermal vents were dominated by brachiopods. Similarly, the pattern of brachiopod vs. bivalve predominance at seeps and vents over the Phanerozoic was believed to have crudely followed that observed in normal-marine benthic shelly assemblages. Recent discoveries from the Middle Palaeozoic of Morocco have questioned this simple perception, documenting the presence of late Silurian and Middle Devonian seeps dominated by mass accumulations of large, semi-infaunal, modiomorphid bivalves (Hryniewicz et al., 2017; Jakubowicz et al., 2017). While representing a lineage unrelated to modern seep-obligate bivalve taxa, the mid-Palaeozoic seep bivalves developed a set of morphological adaptations strikingly similar to those of their modern ecological counterparts, and formed analogous, densely-packed, nearly monospecific assemblages, both suggesting their chemosymbiotic lifestyle. The new documentation of Palaeozoic establishment of the bivalve-dominated seep communities provides a fresh look at the concept of modern chemosynthetic ecosystems as a 'glimpse of antiquity', showing that although it is largely not true taxonomically, it clearly is in terms of recurring morphological themes. At the same time, this refined Palaeozoic record makes the factors responsible for the apparent scarcity of seep-related bivalves during the upper Devonian to early Mesozoic, a period of the remarkable success of brachiopod-dominated seep assemblages, ever more enigmatic.

How to cite: Jakubowicz, M. and Hryniewicz, K.: Are modern chemosynthesis-based communities a ‘glimpse of antiquity’? The changing fate of bivalves and brachiopods at ancient methane seeps as recorded in the Middle Palaeozoic of Morocco, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22640, https://doi.org/10.5194/egusphere-egu2020-22640, 2020.

EGU2020-20678 | Displays | SSP1.3

Macrobenthic community response to long-term climate change in the Adriatic Sea (Italy)

Daniele Scarponi, Michele Azzarone, Rafal Nawrot, and Michal Kowalewski

The ecological consequences of climate change on marine ecosystems remains poorly understood, particularly for ecological communities that reside in enclosed basins, which limit marine species in their ability to migrate. Here we use assemblages of late Quaternary fossils mollusks preserved in nearshore sediments to explore how nearshore marine benthic communities responded to past climate changes in the northern Adriatic.   We focus on three time periods: (1) the last interglacial (<125ka BP), when regional temperatures were higher than today, representing a possible analogue for the near-future global warming; (2) the last late glacial 14.5-18.0 ka BP; and (3) the mid-Holocene 6.0-1.0 ka BP, when conditions were similar to today but with a minimal human impact. Temporal dynamics of benthic communities was assessed by applying multivariate and resampling approaches to abundance data for core-derived samples of fossil mollusks. Results demonstrate that the penultimate interglacial benthic assemblages shifted to a new community state during the subsequent glacial period. The shift represented a decline in abundance of exclusively Mediterranean nearshore species and a concurrent increase in abundance of nearshore species of cosmopolitan and boreal affinity. This shift was, most likely, driven by global climate cooling. Following this major community restructuring, the local nearshore communities had reversed back to their previous state during the mid-Holocene, when interglacial climate conditions were fully reestablished again. We conclude that the nearshore community responded to long-term climate changes by displaying a resilient (rather than persistent or stochastic) behavior, with Holocene biota reversing back to the pre-existing interglacial state. However, regional pollution, trawling and the threat of spreading invasive species are already taking their toll and the present-day communities are shifting to a novel, historical unprecedented community state. Nonetheless, our findings indicate that if local and regional threats can be mitigated, the coastal marine communities of the northern Adriatic would be resilient against limited climate warming in the near future.

How to cite: Scarponi, D., Azzarone, M., Nawrot, R., and Kowalewski, M.: Macrobenthic community response to long-term climate change in the Adriatic Sea (Italy), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20678, https://doi.org/10.5194/egusphere-egu2020-20678, 2020.

EGU2020-650 | Displays | SSP1.3

Micropredators skulking in Silurian oceans?

Isabella Leonhard, Bryan Shirley, Duncan Murdock, and Emilia Jarochowska

Predation is potentially one of the most impactful evolutionary traits to have ever developed. Conodonts, an extinct group of early vertebrates, developed the first phosphatic dental tools, known as elements. Elements ranged from simple coniform types to more complex morphologies, predominantly in more derived species. Unlike the teeth of other vertebrates, these continuously grew throughout their lifetime by the periodic accretion of new lamellar tissues. This unique growth process continuously records chemical and physical characteristics throughout its lifespan which, when accessed, gives direct insight into the animal’s ecology and mode of life. Multiple lines of evidence, such as microwear studies and growth allometry, indicate that adult conodonts fed as predators and/or scavengers. There is little direct independent evidence for feeding ecologies in the earliest conodonts with coniform elements apparatuses, although previous modelling of element position and mechanical properties indicate these were capable of processing or manipulation of food. A direct test would be provided through evidence of tissue damage and its chemical composition. Our research focuses on samples of the coniform genus Panderodus (Family: Panderodontidae) from the Silurian of Poland and Ukraine. Panderodus has the best constrained apparatus reconstruction of any coniform conodont. Here we employ Backscatter electron (BSE) imaging and Energy-dispersive X-Ray spectroscopy (EDX) to identify growth dynamics, microwear, and chemical sclerochronology recorded within this unique mode of growth. Our results have direct implications not just for understanding the feeding mode of Panderodus, but also the origination of predation in the earliest vertebrates in the fossil record.

How to cite: Leonhard, I., Shirley, B., Murdock, D., and Jarochowska, E.: Micropredators skulking in Silurian oceans?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-650, https://doi.org/10.5194/egusphere-egu2020-650, 2020.

EGU2020-950 | Displays | SSP1.3

High-resolution assessment of the Valgu event: conodont diversity and δ18Ophos during the early Telychian (Silurian) in the Baltic Basin

Monica Alejandra Gomez Correa, Emilia Jarochowska, Peep Männik, Axel Munnecke, and Michael Joachimski

The influence of global climate and oceanographic system dynamics over biological patterns throughout Earth’s history is one of the main concerns in paleobiology. Periods that record changes in biodiversity of various magnitude are of particular interest in this field. Previous studies of major Silurian bioevents (e.g. Ireviken, Mulde and Lau) suggest that these events affected different faunas and have been correlated with positive carbon isotope (δ13Ccarb) excursions and positive shifts in oxygen isotopes (δ18Ophos) ratios, suggesting there was a disturbance in the carbon cycle, a drop in temperature, and potential glaciations. However, the impact of the biological events has not been fully assessed, and the influence of climate change remains unclear.

Here, we focus on the Valgu event, a minor episode of proposed environmental and faunistic changes in the early Telychian, which has been recognized in Baltica and Laurentia paleocontinents by changes in conodont succession and a positive excursion in δ13Ccarb. In this study, we assess a limestone-marl alternation core section in Estonia deposited below the storm wave base during the Valgu event. We test for a substantial decrease in the biodiversity of conodont communities, for extent perturbation in the carbon cycle, manifest in a positive δ13Ccarb excursion, and an abrupt positive δ18Ophos shift, which might be indicative of rapid cooling and a rapid sea-level fall typical for glacio-eustatic cycles. To this aim, we measured bulk-rock δ13Ccarb as well as δ18Ophos in monogeneric conodont samples and analyzed the conodont diversity from the event interval.

The lower part of the investigated section is characterized by shallow-water bioclastic limestones containing green algae. On top of this facies, a pronounced hardground indicates a gap in deposition and marks the boundary between the bioclastic limestones and the overlying sediments composed of nodular limestones and marls, which were deposited below the storm wave base. They show a positive carbon shift of ca. 1.4 ‰ during the Valgu interval, but no indication of an extreme change in the conodont biodiversity is evident. Likewise, the δ18Ophos in conodonts remains constant in the section, arguing against cooling or glacially-driven sea-level fluctuations as drivers for the observed changes.

How to cite: Gomez Correa, M. A., Jarochowska, E., Männik, P., Munnecke, A., and Joachimski, M.: High-resolution assessment of the Valgu event: conodont diversity and δ18Ophos during the early Telychian (Silurian) in the Baltic Basin, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-950, https://doi.org/10.5194/egusphere-egu2020-950, 2020.

EGU2020-1057 | Displays | SSP1.3

You Are Where You Live: Using the size of conodont dental tools to shed light on environmental conditions and community complexity

Laura Mulvey, Bryan Shirley, Fiona Pye, Nussaïbah B. Raja, and Emilia Jarochowska

One of the most versatile tools in a palaeontologists’ “tool-kit” is body size analysis, which can be used to characterise and quantify a wide range of ecological and physiological traits.  Utilisation of these data allows insight into predator prey relationships, respiration rates, mortality rates, and even population dynamics. Body size analysis becomes essential when studying extinct organisms where few other clues to their ecology are available. An extreme example of such organisms are conodonts, which are hypothesised to be among the first predators.  Here, changes are tracked  through the Silurian Period using coniform conodont elements as a proxy for body size. Previous research focuses primarily on species turnover, however the data collected in this study is independent of species identification, relying purely on body size changes to reflect the ecology of the community. The size of coniform elements are measured across a number of bathymetries spanning approximately 10 million years. This allows a comparison of body size change not only across differing environments, but also through time. The morphometric measurements were determined using FossilJ, a plugin for ImageJ which facilitates semi-automated measurement of two-dimensional images. Firstly, our results show a clear correlation between body size change and onshore offshore gradients with smaller organisms residing at shallower water depths, unlike what is seen in today’s oceans. Secondly, specimens span across two of the three recorded isotopic excursions during the Silurian Period, the Mulde and Lau events. The impact of these events on conodont communities is represented by a reduction in body size directly after each. Furthermore, the results suggest the Mulde event may have had a stronger effect on these communities and could potentially reflect a time of stress and/or extinction for coniform conodonts.

How to cite: Mulvey, L., Shirley, B., Pye, F., B. Raja, N., and Jarochowska, E.: You Are Where You Live: Using the size of conodont dental tools to shed light on environmental conditions and community complexity, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1057, https://doi.org/10.5194/egusphere-egu2020-1057, 2020.

EGU2020-21707 | Displays | SSP1.3

Determinants of Mollusk Abundance in Quaternary cores of Po Basin, Italy

Michał Kowalewski, Rafał Nawrot, Daniele Scarponi, and Michele Azzarone

Absolute abundance of fossils observed in cores and outcrops can be governed by extrinsic processes (e.g., net accumulation rates, intensity of taphonomic processes, post-mortem transport), intrinsic determinants of shell production rates (e.g., fecundity, spawning frequency, growth patterns), or some combination of those interdependent factors. Understanding the role of drivers of fossil abundance can enhance stratigraphic and biological interpretations of the fossil record. To assess the importance of extrinsic and intrinsic processes for fossil mollusks, we used a total of over 400 samples (each representing a 10-cm core interval and ∼0.375 dm3 of sediment) derived from 12 cores from the late Quaternary sedimentary succession of the Po basin (Italy). The results indicate that although extrinsic factors such as compaction, net accumulation rates, and sequence stratigraphic context are to some degree controlling mollusk abundance in the cores, they cannot account for extremely shell-rich deposits. The results suggest instead that shell-rich core intervals record, primarily, episodes of high shell production rates. First, samples with very high shell density (> 4000 specimens per dm3) were characterized by extremely low evenness reflecting dominance by one super-abundant species, typically a small r-selective species capable of an explosive population growth (Lentidium mediterraneum and Ecrobia ventrosa). Second, a taphonomic test supported further the biological (R-hardparts model) rather than sedimentological (R-sediment model) origin of very dense shell concentrations: the quality of shell preservation correlates positively with shell density as predicted by R-hardparts model. The results suggest that intervals of high abundance of mollusk shells in cores record intervals of high biological productivity driven by opportunistic shelly species from lower trophic levels. Integrative studies of facies architecture, sequence stratigraphy, and paleontological data can help to differentiate biologically and physically produced fossil concentrations thus allowing for more informed ecological interpretations of the fossil record.

How to cite: Kowalewski, M., Nawrot, R., Scarponi, D., and Azzarone, M.: Determinants of Mollusk Abundance in Quaternary cores of Po Basin, Italy, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21707, https://doi.org/10.5194/egusphere-egu2020-21707, 2020.

EGU2020-9349 | Displays | SSP1.3

Microbial regeneration and respiration of Fe(III) outcompetes sulphate respiration in ferruginous, high-sulphate oligotrophic ecosystems

Ingrid Steenbergen, Roman Špánek, Dagmara Sirova, Jakub Borovec, and Daniel Petrash
 

In anoxic lacustrine systems, at low-sulphate concentrations, sulphidisation acts as a crucial pathway driving the reductive dissolution of amorphous and nanocrystalline Fe-(oxyhydr)oxides in the presence of dissolved organic matter. The cycling of intermediate sulphur through a disproportionation reaction with the available Fe(III) stocks supports a continued intermediate sulphur-based respiration mechanism often referred to as cryptic. The prevalence of the so-called cryptic mechanism in meromictic, low-sulphate lakes could be attributed to the abundance of crystalline as opposed to more reactive amorphous iron (oxyhyd)roxides, which by immobilizing ferric iron also favour microbial sulphate reduction (MSR) promoting the accumulation of solid phase intermediate sulphur and sulphides[1]. In a ferruginous, sulphate-rich and oligotrophic post-mining lake (Lake Medard, Czech Republic) we observed a departure from this condition as dissolved sulphide does not accumulate in the bottom water column nor precipitate in the anoxic sediments.[2] Analyses of the bacterioplankton abundance in the hypolimnion indicate a marked niche compartmentalization, with Fe(II)-oxidising microbes, such as Gallionella sp., Rhodopseudomonas sp. and Sideroxydans sp., being important at the dysoxic to anoxic (ferruginous) interface where they drive the regeneration of ferric iron. On the other hand, Fe(III)-reducers, such as Geobacter sp. and Rhodoferax sp. are present at the O2-depleted monimolimnion and in the uppermost anoxic sediments. Toward the redox interface, the chemolithotrophic community described above allows for Fe-(re)cycling and drives the oxidation and turnover of the scarcely available volatile fatty acids. Sulphate reducers (e.g. Desulfobulbaceae, Chrostridia, Desulfarculus) and microorganisms capable of anammox, such as Nitrosomonas  and Nitrosospira where found below the redoxcline. However, together these obligate anaerobes account for < 4% of the total bacterial OTUs identified in the monimolimnion. Our observations in this purported modern analogue to ferruginous, relatively sulphate-enriched Precambrian coastal zones raise the possibility that limited dissimilatory sulphate reduction in the Earth’s primitive ferruginous oceans was rather linked to the scarcity of suitable organic substrates and high rates of Fe-(re)cycling than to low levels of dissolved sulphate. The co-precipitation of minor amounts of gypsum/anhydrite and siderite, with Fe(II,III)-(oxyhydr)oxides further support a potential link between the deep Lake Medard precipitation environment and certain mid- to Late-Archean marginal settings, where these phases have been described to be primary and/or early diagenetic in origin. 

[1] Hansel, C.M., Lentini, C.J., Tang, Y., et al. ISME J. 9, 2400–2412 (2015). 

[2] Petrash, D.A., Jan, J., Sirová, et al. Environ. Sci. Process. Impacts 20, 1414–1426 (2018). 

 

How to cite: Steenbergen, I., Špánek, R., Sirova, D., Borovec, J., and Petrash, D.: Microbial regeneration and respiration of Fe(III) outcompetes sulphate respiration in ferruginous, high-sulphate oligotrophic ecosystems , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9349, https://doi.org/10.5194/egusphere-egu2020-9349, 2020.

EGU2020-7245 | Displays | SSP1.3

Current palynological pattern of steppe-tundra at the Altai highland depressions

Ivan Strelkov, Ekaterina Nosevich, Mikhail Amosov, and Kirill Chistyakov

The landscape and climate research in Altai highlands were carried out in 2018 – 2019. The results of our investigation at the Khindiktig-Khol’ Lake Basin (Mongun-Taiga massif, Tuvan Republic) and Bertek depression (plateau Ukok, Altai Republic) are presented. In frame of study 75 samples (56 – subfossil, 13 flower buds, 6 recent) were collected for pollen analysis. Two key questions are to define the possible steppe-tundra palynological pattern based on project BIOME 6000 relying on steppe and tundra data and to compare palynological pattern with the subfossil data from Altai expeditions (2018-2019). The study was financially supported by Russian Foundation for Basic Research (RFBR) (Grant 18-05-00860).

Within international investigation project BIOME 6000 the palynological patterns of tundra and steppe vegetation were composed (Bigelow et al., 2003). Tundra is characterized by several biomes, such as low- and high-shrub tundra (SHRU; Alnus fruticosa, Betula nana, Salix vestita, Eriophorum, Sphagnum), erect dwarf-shrub tundra (DWAR; Betula nana, Salix herbacea, Cassiope, Empetrum, Vaccinium, Poaceae, Cyperaceae), prostrate dwarf-shrub tundra (PROS; Salix herbacea, Dryas, Pedicularis, Asteraceae, Caryophyllaceae, Poaceae, true mosses), cushion-forb tundra (CUSH; Draba, Papaver, Caryophyllaceae, Saxifragaceae, lichens, true mosses) and graminoid and forb tundra (DRYT; Artemisia, Kobresia, Asteraceae, Brassicaceae, Caryophyllaceae, Poaceae, true mosses). Steppe is described by two biomes: temperate grassland (STEP; Asteraceae, Chenopodiaceae, Liliaceae, grasses) and temperate xerophytic shrubland (STEP; Artemisia, Chrysothamnus, Hippophae, Purshia, grasses). In spite of the absence of steppe-tundra palynological pattern, it may include the pollen data both from steppe (Artemisia, Chrisotamnus, Hippophae, Kobresia, Purshia, Brassicaceae, Chenopodiaceae) and tundra (Alnus fruticosa, Betula nana, Salix herbacea, Cassiope, Draba, Dryas, Empetrum, Eriophorum, Papaver, Pedicularis, Vaccinium, Cyperaceae, Saxifragaceae, Sphagnum, lichens) patterns.

In pollen spectra of western Mongun-Taiga trees mean values vary from 36.4% to 45.4%. The predominance of dwarf birch (Betula nana) dust with the average number 28.7% is identified. As for the Bertek depression, the values change from 36.4% in Muzdy-Bulak to 59.3% in Argamdzhi (2019). Data from subfossil samples in 2018 show the dominance of Betula nana pollen (23.0%), whereas in 2019 it is indicated the significant and constant wind drift of Betula sect. Albae particles (average number – 36.7%) through the massif valleys to the region of sample collection.

In pollen spectra of herbs in Mongun-Taiga region mean value equals 57.9%, whereas at the Bertek depression the values differ from 62.8% (2018) to 37.3% (2019). Those spectra mostly consist of dust samples, such as Carex, Cyperaceae and Poaceae. Asteraceae, Caryophyllaceae, Chenopodiaceae and Fabaceae are also present in both regions.

Artemisia and Chenopodiaceae are the prime indicators of steppe conditions. The vegetation description of the landscapes, where the subfossil samples were collected, proves those conditions. Both vegetation and pollen data are also correlated with the DRYT and STEP biomes from project BIOME 6000. The only difference is that Artemisia prevails at the steppe sites of central and eastern part of Bertek depression, whereas Chenopodiaceae is mostly found within the coexistence of tundra and steppe cenoses in Khindiktig-Khol’ area and western part of Bertek depression.

How to cite: Strelkov, I., Nosevich, E., Amosov, M., and Chistyakov, K.: Current palynological pattern of steppe-tundra at the Altai highland depressions, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7245, https://doi.org/10.5194/egusphere-egu2020-7245, 2020.

EGU2020-7873 | Displays | SSP1.3

The impact of the Pliensbachian-Toarcian crisis on belemnite diversity and size distribution

Kenneth De Baets, Patrícia Rita, Luís Vítor Duarte, Pascal Neige, Laura Piñuela, José Carlos García-Ramos, and Robert Weis

The Pliensbachian–Toarcian transition has been considered a major bottleneck in the early evolution of belemnites, probably related to major palaeoenvironmental and climatic changes during the Early Toarcian. Previous research has focused on the study of belemnites from higher, temperate latitudes, while high-resolution studies on diversity and size of subtropical belemnite assemblages in the northwest Tethys are comparatively rare. The lack of high-resolution (ammonoid subzone) abundance data on diversity and size distributions of belemnite assemblages does not allow separating changes during the Pliensbachian–Toarcian boundary event from those during the Toarcian anoxic event. Sample standardized diversity analyses on new data from Iberian sections suggest the Pliensbachian–Toarcian corresponds to a slight decrease in diversity and an adult size decrease within dominant species. Cluster and non-metric multidimensional scaling analyses, however, indicate that the largest changes in diversity and palaeogeographic distribution of belemnite assemblages occurred during the Toarcian oceanic anoxic event (TOAE) rather than the Pliensbachian–Toarcian boundary. In southern basins like the Lusitanian Basin and Riff Mountains, belemnites even disappear entirely during the TOAE. More generally, the TOAE corresponds with an increase in body size of belemnite assemblages driven by species turnover. The lack of widespread anoxia in southern basins of the northwest Tethys indicates that direct impact of warming or increased pCO2 triggered by volcanism as well as indirect effects on nutrient availability and productivity might have played an important role during both crises.

How to cite: De Baets, K., Rita, P., Duarte, L. V., Neige, P., Piñuela, L., García-Ramos, J. C., and Weis, R.: The impact of the Pliensbachian-Toarcian crisis on belemnite diversity and size distribution, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7873, https://doi.org/10.5194/egusphere-egu2020-7873, 2020.

EGU2020-7994 | Displays | SSP1.3

Optimization of SIMS-based stable isotope measurements with regression diagnostics

Martin Schobben and Lubos Polerecky

Stable isotope measurements with secondary ion mass spectrometry (SIMS) have become an increasingly popular tool for Earth scientists to investigate natural phenomena such as biomineralization and sediment diagenesis, or to track the fate of labelled tracers in stable isotope probing experiments. The random nature of secondary ions emitted from a sample is described by Poisson statistics, which can be used to predict the precision of SIMS measurements under ideal circumstances (e.g., the predicted standard error can be deduced from the total counts of secondary ions). However, besides this fundamental source of imprecision, real SIMS measurements are additionally affected by other factors such as sample heterogeneity, instrument instability, the development and geometry of the sputter pit, and sample charging. Although some of these biases can be avoided by proper instrument tuning and sample documentation (e.g. T/SEM to characterise the textural properties of a rock sample) prior to SIMS measurement, factors such as instrument instability or sample heterogeneity can never be fully eliminated. Here we propose a data treatment procedure capable of identifying the underlying cause of the loss of precision due to instrument instability and sample heterogeneity. The reduced chi-squared statistic, which compares the predicted precision with the precision derived from descriptive statistics, is traditionally used to flag problematic measurements but without pinpointing the cause of precision-loss. We constructed a more sensitive method by the application of regression diagnostics, which calculates the influence of outliers on the regression model, and thus allows for augmentation of the raw count data. Simulations show that the recalculated descriptive and predictive statistics deviate from the original precision along trajectories specific to sample heterogeneity and instrument instability. Thus the proposed diagnostic procedure increases information yield of SIMS isotope measurements.

How to cite: Schobben, M. and Polerecky, L.: Optimization of SIMS-based stable isotope measurements with regression diagnostics, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7994, https://doi.org/10.5194/egusphere-egu2020-7994, 2020.

EGU2020-9271 | Displays | SSP1.3

Pliocene-Pleistocene stratigraphic paleobiology at Altavilla Milicia (Palermo, Sicily): tectonic, climatic and eustatic forcing

Stefano Dominici, Marco Benvenuti, Vittorio Garilli, Alfred Uchman, Francesco Pollina, and Arpad David

The integration of sedimentary facies analysis, ichnology and benthic mollusc quantitative paleoecology allowed to interpret factors controlling deposition of the Altavilla Milicia alluvial to marine succession, near Palermo, Sicily. Two major composite units are recognised, separated by an angular unconformity and internally subdivided into elementary depositional sequences. Calcareous nannoplankton biostratigraphy allowed to recognize the upper Pliocene and lower Pleistocene, a time interval that covers the onset of the Quaternary glaciation. The main asset of the succession is driven by tectonic compression and accommodation by transpressional faults, a regime that led to a change in the direction of fluvial sediment delivery, from axial to transverse with respect to the basin elongation. High-frequency eustatic changes have driven the formation of elementary depositional sequences. The upper Piacenzian is characterised by marine bioclastic strata, deposited during maximum flooding intervals of the two large composite units. Mixed carbonate-siliciclastic lithosomes show a good correlation with shallow marine shell-rich detrital carbonates of Northern and Southern Italy and with Mediterranean deep-water sapropel clusters, suggesting common climatic forcing. Some tropical species previously thought to disappear from the Mediterranean at around 3.0 Ma, are instead present in the upper Piacenzian of Sicily. The study suggests that the Pliocene macrobenthos with tropical affinities disappeared from different sectors of the Mediterranean at different times.

How to cite: Dominici, S., Benvenuti, M., Garilli, V., Uchman, A., Pollina, F., and David, A.: Pliocene-Pleistocene stratigraphic paleobiology at Altavilla Milicia (Palermo, Sicily): tectonic, climatic and eustatic forcing, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9271, https://doi.org/10.5194/egusphere-egu2020-9271, 2020.

EGU2020-10213 | Displays | SSP1.3 | Highlight

Primary productivity, deoxygenation, and the Gulliver-absence effect determine bivalve body size following the end-Permian mass extinction

Melanie Tietje, William J. Foster, Jana Gliwa, Clara Lembke, Autumn Pugh, Richard Hofmann, Sara Varela, Louise C. Foster, Dieter Korn, and Martin Aberhan

The impact of mass extinctions on the body sizes of animals has received considerable attention and debate, as to whether the reduced size of post-extinction organisms is due to the selective extinction of large species, absence of large species as a stochastic effect of low-diversity faunas, or a size decrease within surviving genera and species. Here, we investigated the body sizes of bivalves following the end-Permian mass extinction event and show that the shell size increase of bivalve genera was driven by both evolutionary and ecophenotypic responses. First, some genera show significant increases in body size with the evolution of new species. Further, the same genera record significant within-species increases in average and maximum body size into the late Induan, indicating that ecophenotypic changes were also involved on long-term body size trends. These increases are associated with invigorated ocean circulation, improved oxygenation of the seafloor, and probably increased food supply.

How to cite: Tietje, M., Foster, W. J., Gliwa, J., Lembke, C., Pugh, A., Hofmann, R., Varela, S., Foster, L. C., Korn, D., and Aberhan, M.: Primary productivity, deoxygenation, and the Gulliver-absence effect determine bivalve body size following the end-Permian mass extinction, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10213, https://doi.org/10.5194/egusphere-egu2020-10213, 2020.

A small but rather unique reef type occurs in the Silurian of Gotland mainly composed of encrusting bryozoans and microbial crusts, forming a complex intergrowth, which can be characterized as bryozoan-rich stromatolites, so-called “bryoliths”. The alternation of bryozoans and microbes is assumingly driven by a repeated change of hostile and more favorable conditions for metazoan growth. The surfaces of the reef bodies are composed of characteristic cauliflower structures, created by bryozoans, which are performing a finger-like growth in every direction. Other common features are bioerosion (mostly by bivalves), enigmatic encrusting echinoderms, a high abundance of organophosphatic fossil remains such as bryozoan pearls and discinid brachiopods, a high abundance of epi- and endobionts, vadose silt, and gypsum pseudomorphs.

Altogether, ten of these special reefs have been identified on Gotland so far. All of them were formed during periods of strong positive δ 13C excursions at the Ireviken and Lau isotope excursions in the early Wenlock and late Ludlow, respectively. The unusual features of the bryoliths as well as their occurrence exclusively during strong positive δ 13C excursions indicate very specific environmental requirements. This leads to the assumption, that whatever caused the isotope excursions also has affected these reef systems. Hence, investigating the bryoliths will hopefully increase our knowledge to what has happened during the – still enigmatic – Silurian stable isotope excursions.

How to cite: Claussen, A. L., Munnecke, A., and Ernst, A.: Bryozoan-rich stromatolites (“bryoliths”) from the Silurian of Gotland and their relation to climate-related perturbations of the carbon cycle, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22300, https://doi.org/10.5194/egusphere-egu2020-22300, 2020.

EGU2020-22617 | Displays | SSP1.3 | Highlight

Extreme reefs: Analyses of modern bryostromatolite ("bryolith") reefs from marginal environments in the Netherlands with comparisons to ancient analogues

George William Harrison, Lene Claußen, Christian Schulbert, and Axel Munnecke

Marginal environments sometimes serve as natural time machines, replicating conditions of ancient environments and thus inducing similar adaptations and symbioses. Few environments are more marginal than the brackish, arsenic and titanium rich, and periodically euxinic ponds found in the Zeeland (Netherlands). These ponds contain layered, stationary bioherms of alternating bryozoans and microbialites (bryostromatolites); similar structures are known from the Late Miocene of the Paratethys and the isotopic excursions in the Silurian as well as recent hypersaline lagoons in Australia. Critical study of the modern bryostromatolites will help paleontologists understand the conditions under which bryostromatolites formed in the past.

This study applied modern methods to analyze the microstructures and minerology of bryostromatolites from the Netherlands. These bryostromatolites contained alternations of Einhornia crustulenta bryozoans and gypsum-cemented microbes. Bryostromatolites formed in distinct stages, alternating between a phase of bryozoan layers and a phase where microbes and cements grew in tandem over the dead bryozoans; this microbial phase likely coincides with temporary anoxia/euxinia. The microbes, tentatively identified as cyanobacteria, showed a thrombolitic texture cemented with gypsum. This gypsum was deposited while the microbes were alive, suggesting they were alive during the euxinic phases and participating in sulfide-based photosynthesis. The bryoliths were otherwise poor in fauna, containing only a few species of mollusks, arthropods, polychaetes, and diatoms. All of these factors highlight the extreme environment under which modern and possibly ancient bryoliths formed.

How to cite: Harrison, G. W., Claußen, L., Schulbert, C., and Munnecke, A.: Extreme reefs: Analyses of modern bryostromatolite ("bryolith") reefs from marginal environments in the Netherlands with comparisons to ancient analogues, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22617, https://doi.org/10.5194/egusphere-egu2020-22617, 2020.

SSP1.4 – Achievements and perspectives in scientific ocean and continental drilling

EGU2020-20880 | Displays | SSP1.4 | Highlight

A Plate Too Far: Lessons Learned and Insight Gained from scientific and operational achievements during IODP Expedition 358 in the Nankai Trough.

Adam Wspanialy, Sean Toczko, Nobu Eguchi, Lena Maeda, Kan Aoike, Tomo Saruhashi, Takehiro Hirose, Matt Ikari, Kyuichi Kanagawa, Gaku Kimura, Masataka Kinoshita, Hiroko Kitajima, Demian Saffer, Harold Tobin, Asuka Yamaguchi, and International Ocean Discovery Program Exp 358 Scientists

IODP Expedition 358 planned to access and sample the subducting plate boundary at the Nankai Trough, Japan, and commenced on 7 October 2018, and ended on 31 March 2019, marking the ultimate stage of the NanTroSEIZE project. The goal was to drill down to the plate boundary fault, about 5 km below the ocean floor, where >8M earthquakes occur regularly at every 100–150 years. The successful completion would have represented the deepest borehole in the history of scientific ocean drilling and ultimately greatly deepen our understanding about fault mechanics, earthquake inception and tsunami generation processes.

The IODP Expedition 358 intended to access the plate boundary fault zone system through deepening the previously drilled and suspended C0002P hole. The original operational objective of the Exp 358 was to reach a total depth of 7267.5 mbrt (+/- 5200 mbsf) in 4 drilled sections. Previous major riser drilling efforts during the IODP Expeditions 338 and 348 advanced the main riser hole at Site C0002 (Hole C0002F/N/P) to 3058.5 mbsf meters below sea floor (mbsf). Extensive downhole logging data and limited intervals of core were collected during those expeditions.

Due to the nature of the drilling operation and the anticipated challenges ahead, JAMSTEC adopted oil & gas industry drilling standards and performed two detailed Drilling Well on Paper (DWOP) workshops as part of the very rigorous preparatory stage. Great deal of time was spent on selecting new and state-of-the-art drilling/circulating techniques, logging tools, bits and drilling fluid formulation including a new mud sealant additive “FracSeal” to make sure borehole integrity issues can be minimized as much as possible. Drilling stages seen implementation of a novel concept of near real-time geomechanics to continuously monitor and assess borehole integrity.

The challenges born from side-tracking near the bottom of the previously drilled Hole C0002P (2014 Exp. 348), proved greater than the multi-disciplinary teams expected and the overall objectives set for Exp.358 were not achieved. Nevertheless, despite the significant problems seen during several attempts, the hole was deepened 204 m. This is a minor success and it is believed, once away from the highly damaged area of the C0002P hole, drilling can produce a high-integrity hole following excellent communication and recommendations between drilling and scientific teams during complex drilling operations, especially in complex environments such as the Nankai Accretionary Prism.

Despite not achieving the ultimate goal of the expedition, the implemented industry drilling standards, real-time surveillance system, real time geomechanics, improved and strict communication protocols, and integrating both scientific and drilling teams have demonstrated their value and should become standard practice during future IODP/ICDP operations.

How to cite: Wspanialy, A., Toczko, S., Eguchi, N., Maeda, L., Aoike, K., Saruhashi, T., Hirose, T., Ikari, M., Kanagawa, K., Kimura, G., Kinoshita, M., Kitajima, H., Saffer, D., Tobin, H., Yamaguchi, A., and Exp 358 Scientists, I. O. D. P.: A Plate Too Far: Lessons Learned and Insight Gained from scientific and operational achievements during IODP Expedition 358 in the Nankai Trough., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20880, https://doi.org/10.5194/egusphere-egu2020-20880, 2020.

EGU2020-10122 | Displays | SSP1.4 | Highlight

ICDP project Drilling the Eger Rift – present status and further plans

Torsten Dahm, Tomas Fischer, Heiko Woith, Pavla Hrubcova, Josef Vicek, Michael Korn, Frank Krüger, Josef Horalek, Tomas Vylita, and ICDP-Eger ScienceTeam

Within the ICDP-Eger drilling project we are developing one of the most modern and comprehensive laboratories at depth worldwide to study the interrelations between the flow of mantle-derived fluids through the crust and their degassing at the surface, the occurrence and characteristics of crustal earthquake swarms, and the relation to the geo-biosphere. The Cheb basin located in the western Eger Rift at the Czech-German border provides an ideal natural laboratory for such a purpose. In October 2016 the ICDP proposal was accepted for complementing two existing shallow monitoring wells with five new, distributed, medium depth (<400 m) drill holes F3 and S1-S4.

The resulting natural laboratory at depth will comprise five drilling sites for studying above mentioned phenomena. The F1-F3 drillings form a unique facility of three wells at one site within an active CO2 mofette of Hartoušov for continuous recordings of fluid composition and fluid flow rate, as well as for intermittent GeoBio fluid sampling. Drillings S1-S4 are planned for seismological monitoring to reach a new level of high-frequency, near source observations of earthquake swarms and related phenomena such as seismic noise and tremors generated by fluid movements. Instrumentation of the seismic wells S1-S3 will include 8-element geophone chains and a bottom-hole broadband sensor. The borehole sensors will be complemented at S1 by small-scale surface array of approximately 400 m diameter to obtain truly 3D-array configurations. If possible, broadband surface stations and other sensors will be added to each drill location.

So far, we have completed drillings at sites S1, S2 and S3, with depth of 402, 480 and 400 m. The drilling of S4 is planned in 2020 at one of the recently discovered Maars at the Czech-German border region. Drilling F3 was completed in September 2019 at a depth of 239 m. It has reached several over-pressurized, CO2 bearing layers. The three boreholes have been connected by underground tubes system to the nearby field laboratory equipped by flowmeters and mass spectrometers allowing for long time precise monitoring of the degassing process. The S1 borehole (Landwust) will be instrumented in January 2020 by a test geophone chain allowing, along with the DAS fibre-optic cable installed behind the casing, to carry out a VSP measurement.

In our presentation we provide information on the status of drillings, sensor installation and plans for the complete monitoring and data handling concept.

How to cite: Dahm, T., Fischer, T., Woith, H., Hrubcova, P., Vicek, J., Korn, M., Krüger, F., Horalek, J., Vylita, T., and ScienceTeam, I.-E.: ICDP project Drilling the Eger Rift – present status and further plans , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10122, https://doi.org/10.5194/egusphere-egu2020-10122, 2020.

EGU2020-8872 | Displays | SSP1.4 | Highlight

IODP Expedition 378 South Pacific Paleogene Climate: New high-resolution high-latitude Cenozoic Section

Ursula Röhl, Deborah J Thomas, and Laurel Childress and the Expedition 378 Science Party

As the world’s largest ocean, the Pacific Ocean is intricately linked to major changes in the global climate system. International Ocean Discovery Program (IODP) Expedition 378 is designed to recover Paleogene sedimentary sections in the South Pacific to reconstruct key changes in oceanic and atmospheric circulation. These cores will provide an unparalleled opportunity to add crucial new data and geographic coverage to existing reconstructions of Paleogene climate and as part of a major regional slate of expeditions in the Southern Ocean to fill a critical need for high-latitude climate reconstructions. Appropriate high-latitude records are unobtainable in the Northern Hemisphere of the Pacific Ocean.

The drilling strategy included a transect of sites strategically positioned in the South Pacific to recover Paleogene carbonates buried under red clay sequences at present latitudes of 40°–52°S in 4650 – 5075 meters of water depth. Due to technical issues we no longer will be able to reach the deeper sites. Therefore, the focus of Expedition 378 will be now to obtain a continuous sedimentary record of a previously single hole, rotary-drilled, spot-cored, classic Cenozoic high-latitude DSDP Site 277 and provide a crucial, multiple hole, mostly APC-cored, continuous record of the intermediate-depth Subantarctic South Pacific Ocean from the Latest Cretaceous to late Oligocene.

How to cite: Röhl, U., Thomas, D. J., and Childress, L. and the Expedition 378 Science Party: IODP Expedition 378 South Pacific Paleogene Climate: New high-resolution high-latitude Cenozoic Section, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8872, https://doi.org/10.5194/egusphere-egu2020-8872, 2020.

EGU2020-12094 | Displays | SSP1.4 | Highlight

The seismogenic zones of an M2.0-5.5 earthquakes successfully recovered in deep South African gold mines: the outcomes and the follow-up plan

Hiroshi Ogasawara, Bennie Liebenberg, Yasuo Yabe, Yuki Yokoyama, Tetsuro Hirono, Devan M. Nisson, Tullis C. Onstott, Thomas L. Kieft, Esta van Heerden, Thomas Wiersberg, Taku Noda, Musa S.D. Manzi, Siyanda B. Mngadi, Raymond J. Durrheim, Yuhji Yamamaoto, Takatoshi Ito, Akio Funato, Martin Ziegler, James J. Mori, and Carsten Dinske and the The ICDP DSeis team

This paper reports on the outcomes of the ICDP drilling into seismogenic zones of M2.0-5.5 earthquakes in South African (SA) gold mines (DSeis; 2017-2018), the follow-up work in 2019, and planned post-drilling activity from 2020 onwards.

In deep SA gold mines, seismogenic zones evolve ahead of thin tabular excavations. Normal faulting prevails because mining enhances the vertical maximum principal stress. At 1km depth at the Cooke 4 mine, we elucidated the evolution of the seismogenic zone with a dense acoustic emission network. In 2017, we successfully recovered both the metasedimentary host rock (mainly quartzite ~2.8 Ga) and samples of the seismogenic zone with well-preserved fracture systems using a triple-tube (BQ 1.5m-long). Subsequent laboratory work investigated critical characteristics of rock-rock friction.

In 2014, an M5.5 earthquake, the largest in deep South African gold mining districts, took place. Dense seismic networks, both on the Earth’s surface and at 2-3 km depth, showed that this event was atypical because it was a sinistral event on an unknown geological structure below the mining horizon in West Rand Group strata (~2.9 Ga). Inversion and back-projection of the ground motion showed complicated but unilateral rupture propagation. The densest population of aftershocks shows a sharp upper cut-off and streaks, both dipping to the south.  Its centroid lies outside the significant main rupture zone. In 2017, we commenced drilling at a site at 2.9km depth in a tension quadrant of the sinistral faulting, several hundreds of meters above the upper fringe of the M5.5 aftershock plane. During 2017-2018, we drilled holes, of a total length of 1.6 km. With a 1.5m NQ triple-tube for the critical section, we could recover the fault materials and the host rock with the seismic fracture system well preserved. Borehole logging and core curation in SA and laboratory work at international organizations, including Kochi Core Center Japan (KCC), followed during 2017-2019. With the geology data mapped on the mining horizons and the legacy seismic reflection data as additional information, the following picture is emerging: (a) transition of the stress regime from normal-faulting to sinistral-faulting; (b) stress localization; (c) heterogeneity in the aftershock distribution as well as the segregation between the main rupture and aftershocks, potentially correlated with significant heterogeneity in mechanical properties; (d) a role of an altered lamprophyre dike; (e) hypersaline brine with salinity even higher than measurements at other deep gold mines, potentially as old as brine found at Kidd Creek mine, Canada; and (f) abiogenic gas and organic carbon.

These data sets allow us to address questions in earthquake and deep-life sciences raised in the ICDP Science Plan (2014-2019). In 2019, the ICDP Executive Committee described DSeis as a ‘successful’ project. To integrate and discuss the outcomes in greater depth and plan additional follow-up work, we are planning a post-drilling workshop in November 2020 or January 2021 at KCC before we return the imported critical section of the core to South Africa.

How to cite: Ogasawara, H., Liebenberg, B., Yabe, Y., Yokoyama, Y., Hirono, T., Nisson, D. M., Onstott, T. C., Kieft, T. L., van Heerden, E., Wiersberg, T., Noda, T., Manzi, M. S. D., Mngadi, S. B., Durrheim, R. J., Yamamaoto, Y., Ito, T., Funato, A., Ziegler, M., Mori, J. J., and Dinske, C. and the The ICDP DSeis team: The seismogenic zones of an M2.0-5.5 earthquakes successfully recovered in deep South African gold mines: the outcomes and the follow-up plan, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12094, https://doi.org/10.5194/egusphere-egu2020-12094, 2020.

EGU2020-4886 | Displays | SSP1.4 | Highlight

Towards a Continuous Cenozoic Arctic Climate Record - A Challenge for IODP Expedition 377 in 2021

Ruediger Stein, Estella Weigelt, Frank Niessen, and Kristen St. John

Although the Arctic Ocean is a major player in the global climate/earth system, this region is one of the last major physiographic provinces on Earth where the short- and long-term geological history is still poorly known. This lack in knowledge is mainly due to the major technological/logistical problems in operating within the permanently ice-covered Arctic region which makes it difficult to retrieve long and undisturbed sediment cores. Continuous central Arctic Ocean sedimentary records, allowing a development of chronologic sequences of climate and environmental change through Cenozoic times and a comparison with global climate records, however, were missing prior to the IODP Expedition 302 (Arctic Ocean Coring Expedition – ACEX), the first scientific drilling in the central Arctic Ocean in 2004. By studying the unique ACEX sequence, a large number of scientific discoveries that describe previously unknown Arctic paleo-environments, were obtained during the last 15 years (for most recent review and references see Stein, 2019a). While these results from ACEX were unprecedented, key questions related to the climate history of the Arctic Ocean remain unanswered, in part because of poor core recovery, and in part because of the possible presence of a major mid-Cenozoic hiatus or interval of starved sedimentation within the ACEX record. Following-up ACEX and its cutting-edge science, a second scientific drilling on Lomonosov Ridge with a focus on the reconstruction of the continuous and complete Cenozoic Arctic Ocean climate history, has been proposed and now scheduled as IODP Expedition 377 "Arctic Ocean Paleoceanography - ArcOP") for late summer/early autumn 2021. Based on new seismic and coring data obtained during Polarstern Expedition PS87 in 2014 (Stein, 2015) and Polarstern Expedition PS115/2 in 2018 (Stein, 2019b), several locations for potential drill sites have been proposed and further optimized. At the primary drill site location, about 230 m of Plio-Pleistocene, 460 m of Miocene, and >200 m of Oligocene-Eocene may be recovered. These new detailed climate records spanning time intervals from the Paleogene Greenhouse world to the Neogene-Quaternary Icehouse world will give new insights into our understanding of the Arctic Ocean within the global climate system and provide an opportunity to test the performance of climate models used to predict future climate change. Within this presentation an update of the primary objectives and the drilling strategy of ArcOP Expedition 377 will be outlined. For further details as well as the drilling proposal we refer to http://www.ecord.org/expedition377/ .

 

Reference:

Stein, R. (Ed.), 2015. Cruise Report of Expedition PS115/2 of the Research Vessel POLARSTERN to the Arctic Ocean in 2014 (http://epic.awi.de/37728/1/BzPM_0688_2015.pdf).

Stein, R. (Ed.), 2019b. Cruise Report of Expedition PS115/2 of the Research Vessel POLARSTERN to the Arctic Ocean in 2018. (https://epic.awi.de/id/eprint/49226/1/BzPM_0728_2019.pdf ).

Stein, R., 2019a. The late Mesozoic-Cenozoic Arctic Ocean climate and sea ice history: A challenge for past and future scientific ocean drilling. Paleoceanography & Paleoclimatology, ,  https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2018PA003433

How to cite: Stein, R., Weigelt, E., Niessen, F., and St. John, K.: Towards a Continuous Cenozoic Arctic Climate Record - A Challenge for IODP Expedition 377 in 2021, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4886, https://doi.org/10.5194/egusphere-egu2020-4886, 2020.

EGU2020-13955 | Displays | SSP1.4

Correlation of core and downhole seismic velocities in high-pressure metamorphic rocks: A case study for the COSC-1 borehole, Sweden

Felix Kästner, Simona Pierdominici, Judith Elger, Christian Berndt, Alba Zappone, Jochem Kück, and Anja Maria Schleicher

Deeply rooted thrust zones are key features of tectonic processes and the evolution of mountain belts. Exhumed and deeply-eroded orogens like the Scandinavian Caledonides allow to study such systems from the surface. Previous seismic investigations of the Seve Nappe Complex have shown indications for a strong but discontinuous reflectivity of this thrust zone, which is only poorly understood. The correlation of seismic properties measured on borehole cores with surface seismic data can help to constrain the origin of this reflectivity. In this study, we compare seismic velocities measured on cores to in situ velocities measured in the borehole. The core and downhole velocities deviate by up to 2 km/s. However, velocities of mafic rocks are generally in close agreement. Seismic anisotropy increases from about 5 to 26 % at depth, indicating a transition from gneissic to schistose foliation. Differences in the core and downhole velocities are most likely the result of microcracks due to depressurization of the cores. Thus, seismic velocity can help to identify mafic rocks on different scales whereas the velocity signature of other lithologies is obscured in core-derived velocities. Metamorphic foliation on the other hand has a clear expression in seismic anisotropy. To further constrain the effects of mineral composition, microstructure and deformation on the measured seismic anisotropy, we conducted additional microscopic investigations on selected core samples. These analyses using electron-based microscopy and X-ray powder diffractometry indicate that the anisotropy is strongest for mica schists followed by amphibole-rich units. This also emphasizes that seismic velocity and anisotropy are of complementary importance to better distinguish the present lithological units. Our results will aid in the evaluation of core-derived seismic properties of high-grade metamorphic rocks at the COSC-1 borehole and elsewhere.

How to cite: Kästner, F., Pierdominici, S., Elger, J., Berndt, C., Zappone, A., Kück, J., and Schleicher, A. M.: Correlation of core and downhole seismic velocities in high-pressure metamorphic rocks: A case study for the COSC-1 borehole, Sweden, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13955, https://doi.org/10.5194/egusphere-egu2020-13955, 2020.

EGU2020-22367 | Displays | SSP1.4 | Highlight

Investigating the Dynamics of the Pacific Antarctic Circumpolar Current – Initial Results from International Ocean Discovery Program Expedition 383 (DYNAPACC)

Frank Lamy, Gisela Winckler, Carlos Zarikian, and Expedition 383 Scientists

The Antarctic Circumpolar Current (ACC) is the world’s strongest zonal current system that connects all three major basins of the global ocean, and therefore integrates, forces and responds to global climate variability. In contrast to the Atlantic and Indian sectors of the ACC, and with the exception of drill cores from the Antarctic continental margin and off New Zealand, the Pacific sector of the ACC lacks information on its Cenozoic paleoceanography from deep-sea drilling records.

To advance our knowledge and understanding of Miocene to Holocene atmosphere-ocean-cryosphere dynamics in the Pacific and their implications for regional and global climate and atmospheric CO2, IODP Expedition 383 recovered sedimentary sequences at: (1) Three sites located in the central South Pacific (Sites U1539, U1540 and U1541); (2) two sites at the Chilean Margin (U1542, U1544); and (3) one site from the hemipelagic eastern South Pacific (U1543) close to the entrance to the Drake Passage. Age control based on magneto and bio-stratigraphically constrained orbital tuning of physical properties in the Plio-Pleistocene sediments is remarkable, with Sites U1541 and U1543 extending the record back to the late Miocene, and Site U1540 to the earliest Pliocene. Pleistocene sedimentary sequences with high sedimentation rates in the order of 40 cm/kyr were drilled in the Central South Pacific (U1539) and along the Chilean Margin. Taken together, the sites represent a depth transect from ~1100 m at the Chilean margin (U1542) to ~4070 m in the Central South Pacific (U1539), and allow reconstructing changes in the vertical structure of the ACC – a key issue for understanding the role of the Southern Ocean in the global carbon cycle- to be investigated. The sites are located at latitudes and water depths where sediments will allow the application of a wide range of siliciclastic, carbonate, and opal-based proxies to address our objectives of reconstructing, with unprecedented stratigraphic detail, surface to deep ocean variations and their relation to atmosphere and cryosphere changes through stadial-to-interstadial, glacial-to-interglacial and warmer than present time intervals.

How to cite: Lamy, F., Winckler, G., Zarikian, C., and 383 Scientists, E.: Investigating the Dynamics of the Pacific Antarctic Circumpolar Current – Initial Results from International Ocean Discovery Program Expedition 383 (DYNAPACC), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22367, https://doi.org/10.5194/egusphere-egu2020-22367, 2020.

In Early Cretaceous, Shahezi Formation developed in syn-rift stage which belongs to the deep strata of the Songliao Basin, China. Due to the poor outcrop development, there is no previous study or report on the provenance of detrital zircons from Shahezi Formation before. The Songke 2 well is a part of Songliao Basin drilling project which belongs to the International Continental Scientific Drilling Projects (ICDP). The conduct of this scientific drilling is to obtain a nearly complete Cretaceous terrestrial sedimentary record, as determined from basin-filling history. Therefore, this research will focus on the sample from Songke 2 well. This study based on continuous and complete sampling which are unique research materials. What’s more, Songliao Basin is one of the largest continental sedimentary basins in the world, which holds the most important reserves of Chinese oil and natural gas. Consequently, this study is a kind of significance for oil and natural gas prospects of deep strata in Songliao Basin.

Through the detailed description about cores, fan delta facies and lacustrine facies can be identified in this study. Also, the detailed information and sedimentary environment at Early Cretaceous can be clarified. The upper member of Shahezi formation shows the characteristics of fan delta facies intersecting shore-shallow lakes, reflecting the multistage cyclicity changes under the sufficient source supply during the syn-rift stage. In order to define the provenance of the upper member of Shahezi Formation in the north-central area of the Songliao Basin, five sandstone sample (DZ01~05) of the upper member of Shahezi Formation were continuous sampling from Songke 2 well. U-Pb dating was performed on detrital zircons separated from the five sandstone samples. Detrital zircons from DZ01 to DZ05 has dominant ages of 105~140 Ma (268 grains), 155~200 Ma (160 grains), and 220~260 Ma (44 grains). This paper demonstrates that the provenance of the upper member of Shahezi Formation is came from the Central Great Xing’an Range. The depositional period of the Shahezi Formation constraints of maximum sedimentary age and reached to 111-115 Ma. At the same time, the Great Xing’an Range also provides sediments for the western Hailar Basin, which indicates that the Great Xing’an Range uplift and denudation during this period. The closure and collision of the Mongolia-Okhotsk ocean to the north and Pacific Plate subduction beneath the Asian continent to the east were the major tectonic events affecting the tectonic environment of the Great Xing’an Range.

How to cite: An, D.: Early Cretaceous (Aptian) provenance and tectonic response in Songliao Basin, NE China: Evidence from detrital zircon U-Pb ages from the Shahezi Formation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5621, https://doi.org/10.5194/egusphere-egu2020-5621, 2020.

EGU2020-7686 | Displays | SSP1.4

Uncharted archives – imprints of tsunami backwash deposits on the Algarve shelf (Portugal)

Piero Bellanova, Klaus Reicherter, Pedro J.M. Costa, Mike Frenken, Lisa Feist, Jan Schwarzbauer, Juan I. Santisteban, Andreas Vött, Ivana Bosnic, Helmut Brückner, Holger Schüttrumpf, César Andrade, João F Duarte, Jannis Kuhlmann, and the M152 scientfic Team

Research on offshore tsunami deposits is scarce and their depositional processes and preservation potential are virtually unexplored. Therefore, the RV Meteor cruise M152 mapped and sampled one coast-parallel and two coast-perpendicular transects at water depths from 65 to 114 m off the Algarve coast (Portugal). This coast was strongly affected by the well-known Lisbon earthquake and tsunami of November 1st, 1755 AD. Numerous onshore locations have been well documented and studied with historic damage reports and modern scientific investigations of the onshore tsunami deposits. However, very scarce information about the backwash, the water masses flowing back into the sea, exists and their imprint on the shelf is unexplored.

In order to fill this gap, a total of 19 vibracores were recovered during the RV Meteor cruise M152. For tracing the sedimentary imprint of the AD 1755 tsunami and potential predecessors, a multi-proxy analysis was carried out (sedimentology, micropaleontology, inorganic and organic geochemistry, radiocarbon and OSL dating). Within the offshore Holocene stratigraphic record, at least two event layers of likely tsunami backwash origin were identified based on their significantly different properties compared to the background shelf sediments. The uppermost tsunami layer (at a depth of 16-25 cm in most cores) displays an erosional contact at the base with heterogeneous compositional changes; its bounding radiocarbon ages allow a correlation with the AD 1755 Lisbon tsunami. Organic-geochemical markers, such as n-alkanes, polycyclic aromatic hydrocarbons, steroids and fatty acids, show an increased input of terrestrial matter in this offshore AD 1755 event layer.

A surprising discovery was another distinct high-energy deposit, i.e. a potential predecessor to the AD 1755 Lisbon tsunami, at a core depth of about 122-155 cm, which was 14C-dated to approx. 3700 yrs cal BP. Due to its erosional base and coarse-grained composition (well-sorted medium sand), as well as the increased terrestrial influence (displayed by biomarkers), it can be assumed that this deposit originates from the backwash of a paleo-tsunami.

This multi-proxy approach with sedimentological, micropaleontological, inorganic and organic-geochemical criteria, enabled us to (1) identify of backwash tsunami deposits; (2) establish a recurrence interval; and (3) estimate the hazard potential for the related coastal areas. Results of the M152 cruise demonstrate for the first time that the depositional basins on the Algarve shelf have the potential to reliably archive Holocene tsunami backwash deposits. The low-energy environment of the outer Algarve shelf sets prime conditions for the preservation of tsunami backwash deposits. Thus, these geoarchives offer the possibility to study the mechanisms and hydrodynamics of backwash currents, and to investigate tsunami strata that are not preserved elsewhere.

How to cite: Bellanova, P., Reicherter, K., Costa, P. J. M., Frenken, M., Feist, L., Schwarzbauer, J., Santisteban, J. I., Vött, A., Bosnic, I., Brückner, H., Schüttrumpf, H., Andrade, C., Duarte, J. F., Kuhlmann, J., and M152 scientfic Team, T.: Uncharted archives – imprints of tsunami backwash deposits on the Algarve shelf (Portugal), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7686, https://doi.org/10.5194/egusphere-egu2020-7686, 2020.

EGU2020-20571 | Displays | SSP1.4

Planning a drilling campaign in a petroleum province using high resolution 3D seismic data – IODP proposal 909

David Cox, Andrew M. W. Newton, Paul C. Knutz, and Mads Huuse

A drilling hazard assessment has been completed for a large area of the NW Greenland-Baffin Bay continental shelf. This assessment was in relation to International Ocean Discovery Program (IODP) proposal 909 that aims to drill several sites across the shelf in an attempt to better understand the evolution and variability of the northern Greenland Ice Sheet. The assessment utilised high quality and extensive 3D seismic data that were acquired during recent hydrocarbon exploration interest in the area – a fact that highlights the risk of drilling in a petroleum province and therefore, the importance of this assessment with regards to safety.

Scattered seismic anomalies are observed within the Cenozoic sedimentary succession covering the rift basins of the Melville Bay region. These features, potentially representing the presence of free gas or gas-rich fluids, vary in nature from isolated anomalies, fault flags, stacked fluid flow features and canyons; all of which pose a significant drilling risk and were actively avoided during site selection. In areas above the Melville Bay Ridge – a feature that dominates the structure of this area – free gas is also observed trapped beneath extensive gas hydrate deposits, identified via a spectacularly imaged bottom simulating reflector marking the base of the gas hydrate stability zone. The location of the hydrate deposits, and the free gas beneath, are likely controlled by a complicated migration history, due to large scale rift-related faulting and migration along sandy aquifer horizons. In other areas, gas is interpreted to have reached the shallow subsurface due to secondary leakage from a deeper gas reservoir on the ridge crest.

It is clear that hydrocarbon related hazards within this area are varied and abundant, making it a more challenging location to select sites for an IODP drilling campaign. However, due to the extensive coverage and high resolution (up to 11 m vertical resolution (45 Hz at 2.0 km/s velocity) of the 3D seismic data available, as well as the use of recently acquired ultra-high resolution site survey lines, these features can be accurately imaged and confidently mapped. This allowed for the development of a detailed understanding of the character and distribution of fluids within the shallow subsurface, and the use of this knowledge to select site localities that maximise the potential for drilling to be completed safely and successfully if proposal 909 were to be executed.

How to cite: Cox, D., Newton, A. M. W., Knutz, P. C., and Huuse, M.: Planning a drilling campaign in a petroleum province using high resolution 3D seismic data – IODP proposal 909, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20571, https://doi.org/10.5194/egusphere-egu2020-20571, 2020.

EGU2020-8069 | Displays | SSP1.4

Extending Ocean Drilling Pursuits [eODP]: Making Scientific Ocean Drilling Data Accessible Through Searchable Databases

Andrew Fraass, Leah LeVay, Jocelyn Sessa, and Shanan Peters

Scientific ocean drilling through the International Ocean Discovery Program (IODP) and its predecessors, has a far-reaching legacy. They have produced vast quantities of marine data, the results of which have revolutionized many geoscience subdisciplines. Meta-analytical studies from these efforts exist for micropaleontology, paleoclimate, and marine sedimentation, and several outstanding resources have curated and made available elements of offshore drilling data (e.g., Neptune), but much of the data remain heterogeneous and dispersed. Each study, therefore, requires reassembling a synthesis of data from numerous sources; a slow, difficult process that limits reproducibility and slows the progress of hypothesis testing and generation. A computer programmatically-accessible repository of scientific ocean drilling data that spans the globe will allow for large-scale marine sedimentary geology and micropaleontologic studies and may help stimulate major advances in these fields.

The eODP project, funded through the NSF’s EarthCube program, seeks to facilitate access to, and visualization of, these large microfossil and stratigraphic datasets. To achieve these goals, eODP will be linking and enhancing the existing database structures of the Paleobiology Database (PBDB) and Macrostrat. This project is targeting shipboard drilling-derived data, but the infrastructure will be put in place to allow the addition of data generated post-cruise. eODP will accomplish the following goals: (1) enable construction of sediment-grounded and flexible age models in an environment that encompasses the deep-sea and outcrops; (2) expand existing lithology and age model construction approaches in this integrated offshore-onshore stratigraphically-focused environment; (3) adapt key microfossil data into the PBDB data model; (4) develop new API-driven web user interfaces for easily discovering and acquiring data; and (5) establish user working groups for community input and feedback. The success of eODP hinges upon interaction, feedback, and contribution of the scientific ocean drilling community, and we invite anyone interested in participating in this project to join the eODP team.

How to cite: Fraass, A., LeVay, L., Sessa, J., and Peters, S.: Extending Ocean Drilling Pursuits [eODP]: Making Scientific Ocean Drilling Data Accessible Through Searchable Databases , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8069, https://doi.org/10.5194/egusphere-egu2020-8069, 2020.

EGU2020-5089 | Displays | SSP1.4 | Highlight

More than ten years of successful operation of the MARUM-MeBo sea bed drilling technology: Highlights of recent scientific drilling campaigns

Tim Freudenthal, Gerhard Bohrmann, Karsten Gohl, Johann Philipp Klages, Michael Riedel, Klaus Wallmann, and Gerold Wefer

Over the last two decades sea bed drilling technology has proven to provide a valuable complement to the services of classical drill ships. Especially for shallow drillings up to 200 mbsf and when working in remote areas difficult to access, sea bed drill rigs are a cost-effective alternative. Recent developments especially concerning borehole logging techniques add to the capabilities of sea bed drilling technology.

The MARUM-MeBo is a robotic drilling system that is developed since 2004 at the MARUM Center for Marine Environmental Sciences at the University of Bremen (Freudenthal and Wefer, 2013). The drill rig is deployed on the sea bed and remotely controlled from the vessel. It is used for core drilling in soft sediments as well as hard rocks in the deep sea. Especially since an upgrade in 2007/2008 for the use of wireline drilling technique, the first-generation drill rig MARUM-MeBo70 with a drilling capacity of about 70 m was successfully deployed on more than 15 research expeditions. Since 2014 the second-generation drill rig MARUM-MeBo200 with an increased drilling capacity of up to 200 m below sea floor is successfully in operation.

In this presentation we focus on results of three recent drilling campaigns, exemplifying the exploitation of the potential of the sea bed drilling technology:

  1. In early 2017 the MeBo70 was deployed from the ice breaking vessel RV POLARSTERN on the West Antarctic shelf (Gohl et al., 2017), an area difficult to access by a drill ship. We were able to recover a sedimentary sequence of the upper Cretaceous time period as one of the very few terrigenous records from this time in Antarctica. This sequence indicates that about 92 to 83 Mio years ago at a paleolatitude of about 82°S this area was covered by a temperate coastal rain forest, making any Antarctic ice sheet formation at this time period unlikely (Klages et al., in press).
  2. Also, in 2017 the MeBo70 was deployed in the Arctic off Svalbard. Next to coring a temperature probe was used to assess in situ temperatures and local geothermal gradients (Riedel et al. 2018). Combining these temperature data with the porewater geochemistry of the drilled cores Wallmann et al (2018) were able to prove the effect of isostatic rebound after deglaciation on gas hydrate dissociation.
  3. In late 2017 the MeBo200 was deployed in the Black Sea. Geophysical borehole log data of P-wave velocity, electrical resistivity, and spectral gamma ray were combined with core-derived physical properties of porosity, magnetic susceptibility, and bulk density and compared with seismic data of the region (Riedel et al., in press). This study shows the potential of core-log seismic integration for shallow drilling campaigns conducted with a sea bed drill rig.

References:

Freudenthal, T and Wefer, G (2013) Geoscientific Instrumentation, Methods and Data Systems, 2(2). 329-337. doi:10.5194/gi-2-329-2013

Gohl, K, et al. (2017) Geochemistry, Geophysics, Geosystems, 18, 4235–4250. https://doi.org/10.1002/2017GC007081

Klages, JP et al. (in press) Nature, 2019-10-14805B

Riedel, M et al. (2018) Geochemistry, Geophysics, Geosystems, 19, 1165–1177. doi:10.1002/2017GC007288

Riedel, M et al. (in press) Marine and Petroleum Geology, doi.org/10.1016/j.marpetgeo.2019.104192

Wallmann, K et al. (2018) Nature Communications, 9:83, DOI: 10.1038/s41467-017-02550-9

 

How to cite: Freudenthal, T., Bohrmann, G., Gohl, K., Klages, J. P., Riedel, M., Wallmann, K., and Wefer, G.: More than ten years of successful operation of the MARUM-MeBo sea bed drilling technology: Highlights of recent scientific drilling campaigns, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5089, https://doi.org/10.5194/egusphere-egu2020-5089, 2020.

EGU2020-13070 | Displays | SSP1.4

Lake Constance sediments recovered using novel piston coring system

Ulrich Harms, Ulli Raschke, Antje Schwalb, and Volker Wittig

Key archives in environmental and past climate research are buried in soft sediment but investigations are often hampered by the lack of continuous, complete and undisturbed samples. We have developed the new core-drilling instrument Hipercorig to overcome these issues and we have tested this tool successfully on the perialpine Lakes Mondsee and Constance at up to 204 m water depths and down to 64 m core length.

Hipercorig comprises a hydraulically hammered down-the-hole piston coring system capable to reach up to 100 m core length in up to 200 m water depths. The well-proven piston system ensures high-quality intact cores while the hydraulic hammer drive allows penetrating hard-layers such as sand, gravel or tephra. The piston-hammer system, casing string and ground plate is connected via Kevlar ropes to a coring rig and deployment is controlled via underwater cameras. For lake, estuarine and shallow marine projects buoyance and working space is provided through a barge with four anchors and winches. The complete system is consisting of modular elements to be shipped in four 20-foot-containers including two boats and outboard motors. Hipercorig allows for about 10 m rate of penetration per shift and produces 7.5 cm cores in 2 m long core runs.

A first deployment on Lake Mondsee to initially test and modify Hipercorig recovered 64 m sediment core from glacial tills. A follow on shake-down cruise on Lake Constance served as deep-water trial and to sample so far unearthed pre-Holocene strata below about 12 m sediment depth. Coring was performed in summer 2019 in 204 m water depth, 2 km SSW of Hagnau, Germany. The site is located close to the deepest part of this basin with best possible preservation of a continuous and undisturbed depositional record. Two sediment cores of 24 and 20.5 mblf were retrieved and complemented by three 2-m-long surface cores. The uppermost 11 m of sediments consist of Holocene lacustrine clays with increasing intercalations of silt, while late Quaternary glacial sands dominate below 11 m. The piston coring device was modified to allow for penetrating these rigid sand layers, but the sands slowed down core recovery and caused core loss of ~15 cm at the end of each core run but overlapping coring was used to compensate the loss. While samples for microbiology have been taken immediately, core opening, description, and sampling will be performed at Bern University, Switzerland, in October 2019.

Currently Hipercorig receives final upgrades for safety and flexibility so that the whole system will be available from spring 2020 on for scientific coring projects on a non-for-profit base to teams with funded research projects. They will have to raise transport and operations costs as well as a maintenance fee that will serve to sustain the tool. The German Scientific Earth Probing Consortium GESEP will provide an oversight board to prioritize projects and support projects in implementation.

How to cite: Harms, U., Raschke, U., Schwalb, A., and Wittig, V.: Lake Constance sediments recovered using novel piston coring system, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13070, https://doi.org/10.5194/egusphere-egu2020-13070, 2020.

EGU2020-4270 | Displays | SSP1.4

Preliminary report on the sedimentary record of SCORE Site C9035 of Tokai, Nankai Trough, southwest Japan

Kan-Hsi Hsiung, Toshiya Kanamatsu, Ken Ikehara, Io Miura, Juichiro Ashi, Shuichi Kodaira, Kohsaku Arai, Natsumi Okutsu, and Kan Aoike

Chikyu Shallow Core Program (SCORE) is a short and shallow ocean drilling program arranged by Japan Drilling Earth Science Consortium (J-DESC), Japan. SCORE provides opportunities for scientific ocean drilling test and project which can complete in a short period of time by using the ocean drilling vessel D/V Chikyu except for IODP expedition period. The title of this project is “Enigmatic recurrence pattern of Tokai earthquake in Nankai Trough, southwest Japan: the link between great earthquakes and ridge subduction”. The objective of our program is to investigate the past earthquake occurrence from a continuous sedimentary sequence at a local tectonic basin (i.e., Kanasunose Trough) in Nankai Trough. The target of this drilling program is to find an enigmatic recurrence pattern of Tokai earthquake in Nankai Trough, southwest Japan. Hydraulic Piston Coring System (HPCS) of the ocean drilling vessel (D/V) Chikyu can provide an opportunity to obtain an excellent long and continuous sedimentary record to unravel the earthquake recurrence pattern of this study area.

 

Expedition 912 was conducted by D/V Chikyu sailing from Shimizu to Sasebo, Japan from 4 January - 15 January 2020. The Leg 1 of Expedition 912 was cored Hole A and B in Site C9035 which are located in 34°05.7’N, 138°08.03’E with 2442 meters of water depth in the Kanasunose Trough, Tokai, Nankai Trough. The Penetration depth at site C9035 is 80.19 meters with HPCS drilled from 5 January to 8 January 2020. The thickness of Hole C9035A sediments was 9.5 m with a recovery of 105%. The thickness of cored sediments was 80.19 meters at Hole C9035B, with a recovery of 104.7%. The shipboard measurements of whole-round core samples involved X-ray CT scan and Physical properties. After splitting, the visual core description (VCD), smear slides, split surface image, Natural Remanent Magnetisation (NRM), penetration strength, and moisture and density (MAD) measurements, and Vane shear test were conducted.

 

The sedimentary succession is dominated by silty sediments with numerous coarse-grained (coarse silt–very fine sand) layers and some volcanic ash layers and spots. Two lithological units (Unit I and II) can be distinguished on the basis of sedimentary facies. Unit I consists of bioturbated silt and layered coarse silt–very fine sand with massive silt. Three ashes can be founded in Unit I and will provide good age control. Unit II is characterized by matrix-supported gravelly mud–muddy gravel and angular mudstone gravel. After measurements, the extended work of the recurrence intervals of seismo-turbidite in geological time will be built to stimulate the link between great earthquakes and ridge subduction.

How to cite: Hsiung, K.-H., Kanamatsu, T., Ikehara, K., Miura, I., Ashi, J., Kodaira, S., Arai, K., Okutsu, N., and Aoike, K.: Preliminary report on the sedimentary record of SCORE Site C9035 of Tokai, Nankai Trough, southwest Japan, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4270, https://doi.org/10.5194/egusphere-egu2020-4270, 2020.

EGU2020-4219 | Displays | SSP1.4

Rift propagation north of Iceland: A case of asymmetric plume - rift interaction?

Hans Christian Larsen, Anett Blischke, and Bryndís Brandsdóttir and the IODP Proposal 976-Pre working group

Drilling by the Ocean drilling Program (ODP Legs 104, 152, 163) and geophysical studies have inferred a widespread and strong influence by the Iceland plume on the structure of the ~2500 km long volcanic rifted margins that formed between East Greenland and NW Europe during continental breakupat  ~56-54 Ma. A persistent, but spatially much reduced impact by the plume on crustal structure is evident along the ~250 km Greenland-Iceland-Faeroe ridge (GIFR). Spreading south of the GIFR has remained comparatively stable along the Reykjanes Ridge (RR). By contrast, spreading between the GIFR and northwards to the Jan Mayen Fracture Zone (JMFZ) involved northward rift propagation (~50-25 Ma) away from the Iceland plume and into the East Greenland margin. This was paired with a northward retreat of the initial spreading axis (Aegir ridge (AER)) further to the east. Slivers of the East Greenland continental crust topped by continental plateau basalts extruded during initial breakup were torn off by this northward rift propagation, and form segments of the Jan Mayen microcontinent (JMMC). Rift propagation resulted in the formation of the Iceland Plateau (IP) underlain by anomalously thick and shallow oceanic crust. The striking asymmetry in plate kinematics and crustal structures south and north of Iceland seems associated with a less enriched mantle source feeding the spreading system north of Iceland. This suggests a potentially long-lived north-south asymmetry in the composition and dynamics of the plume that, if confirmed, will favor the existence of distinctly different mantle reservoirs rather than a mixing (entrainment) process followed by a compositional de-convolution process during decompression melting and melt distribution. IODP proposal 976-Pre will address these topics by investigating the temporal and compositional development of the crust of the IP, as well as the transition from rift propagation by the IP rift (IPR) into the present day Kolbeinsey ridge (KR). Drilling will sample 2-3 stages of four IPR propagation stages we have mapped, the transition from the IPR to KR spreading, rifting and timing of transpressive movements along the pseudo-transform zone that linked the propagating IPR to the retreating AER. One drill site hopefully will establish the stratigraphic relationship between the JMMC basalts and the East Greenland plateau basalts. Sediment cover at the drill sites will constrain subsidence history and the paleo-environmental evolution of the high-latitude north-east Atlantic and its connectivity to the global ocean.The proposed drilling addresses long-standing ocean drilling themes of continental breakup, rift propagation, mantle plume reservoirs and structure, and north Atlantic paleoceanography.

How to cite: Larsen, H. C., Blischke, A., and Brandsdóttir, B. and the IODP Proposal 976-Pre working group: Rift propagation north of Iceland: A case of asymmetric plume - rift interaction?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4219, https://doi.org/10.5194/egusphere-egu2020-4219, 2020.

EGU2020-19204 | Displays | SSP1.4

Indian subcontinent hydroclimate and vegetation changes during the last glacial reconstructed by leaf wax stable isotope and pollen analyses on sediments from IODP Site U1446, NW Bay of Bengal

Stefan Lauterbach, Nils Andersen, Charlotte Clément, Stéphanie Desprat, Coralie Zorzi, Krishnamurthy Anupama, Srinivasan Prasad, Dulce Oliveira, Thomas Blanz, Kaustubh Thirumalai, Steven C. Clemens, Philippe Martinez, and Ralph R. Schneider

Understanding past variability and forcing mechanisms of the Asian monsoon system is of key importance for better forecasting its behaviour under future global warming scenarios and how this may affect modern societies and economies. So far, knowledge about long-term monsoon variability in mainland Asia is mainly based on proxy records from Chinese speleothems, primarily recording changes of the East Asian Summer Monsoon (EASM). These records have provided evidence for orbital-scale monsoon variability, driven by Northern Hemisphere summer insolation changes, but also for centennial- to millennial-scale reductions in monsoon precipitation. These so-called Weak Monsoon Intervals (WMIs) occurred synchronously to cold intervals in the North Atlantic realm, e.g. during Heinrich Events, pointing at a close hemisphere-scale climatic teleconnection between the North Atlantic and Asia. However, the exact mechanisms that control short-term monsoon variability are still elusive. Moreover, long-term palaeomonsoon proxy records from the core zone of the Indian Summer Monsoon (ISM) are still relatively scarce compared to those from the EASM realm. To identify possible short-term changes in ISM intensity and reconstruct related hydroclimate and vegetation changes on the Indian subcontinent during the interval ~6–74 ka BP, sediments from IODP Site U1446 in the NW Bay of Bengal have been analysed. This site, being located within the reach of the Mahanadi River, is characterized by high riverine input of terrestrial organic matter and thus ideal for high-resolution analyses of pollen content and the stable hydrogen (δD) and carbon (δ13C) isotope composition of n-alkanes from terrestrial plant leaf waxes. Here we present preliminary results of δD and δ13C analyses on odd-numbered long-chain n-alkanes (n-C27 to n-C33,) extracted from the IODP Site U1446 sediments. These indicate several reductions in ISM precipitation during the last glacial, which occurred parallel to cold events in the North Atlantic realm, e.g. during Heinrich events H1, H2, H4, H5 and H6. In combination with pollen and alkenone-based (UK’37) sea surface temperature data from the same sediments, we aim at (1) providing a comprehensive and high-resolution reconstruction of past ISM variability and associated vegetation changes on the Indian subcontinent and (2) understanding the trigger mechanisms of centennial- to millennial-scale WMIs, particularly in relation to changes in Indian Ocean oceanography.

How to cite: Lauterbach, S., Andersen, N., Clément, C., Desprat, S., Zorzi, C., Anupama, K., Prasad, S., Oliveira, D., Blanz, T., Thirumalai, K., Clemens, S. C., Martinez, P., and Schneider, R. R.: Indian subcontinent hydroclimate and vegetation changes during the last glacial reconstructed by leaf wax stable isotope and pollen analyses on sediments from IODP Site U1446, NW Bay of Bengal, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19204, https://doi.org/10.5194/egusphere-egu2020-19204, 2020.

EGU2020-10110 | Displays | SSP1.4

Drilling the Tore seamount- Archive of a natural oceanic sediment trap

Susana M. Lebreiro, Silvia Nave, Laura Antón, Elizabeth Michel, Catherine Kissel, Claire Waelbroeck, Nick McCave, David Hodell, Jose-Abel Flores, Francisca Martinez-Ruiz, Belén Martrat, Cristina Roque, Alex Piotrowski, Luke Skinner, Francisco Sierro, Pedro Terrinha, Guy Cornen, María Isabel Reguera, Rocío Lozano-Luz, and Natalia Bravo

Located 300 km off West Iberia in the open NE Atlantic Ocean, the Tore seamount emerges from the 5.5 km surrounding abyssal plains to a summit rim at 2.2 km, which has an elliptical crater-like shape with a central depression 100 km in diameter. The ~5.5 km depth of the Tore internal basin is connected to the surrounding deep ocean basin by a single narrow gateway down to 4.3 km depth. This basin is exceptional because it is 1) a giant sediment-trap for vertical fluxes, with sediments unaffected by deep currents and erosion, containing a record of enhanced biogenic subtropical productivity during deglaciations, which can be examined mechanistically, 2) a natural laboratory to examine carbonate dissolution at 5.5 km water depth constrained by NADW deep ventilation during glacials, and 3) an excellent location to test sediment processes distant from continental margins and understand triggering mechanisms of downslope flows in the open, deep ocean. Not many cores have been recovered in the area at such 5.5 km depth and unite this singular environment. At the larger scale of North Atlantic circulation and productivity, the semi-isolated Tore seamount is a most valuable site to assess crucial scientific hypotheses related to thermohaline circulation, carbon cycling and climate variability. These challenging questions are framed in the IODP Initial Science Plan illuminating Earth´s Past, Present and Future, 2013-2023, theme Climate and Ocean Change.

Our APL applies for drilling one site in the middle of the Tore seamount at 5.5 km depth, to retrieve a complete Quaternary sedimentary sequence (180 m long). This carbonate rich archive will be compared with records available in the Northeast Atlantic and to be recovered during Expedition #771-Full2 (Hodell et al.).

We present results from a 24 long giant Calypso core taken in the APL-site proposed which covers 430 thousand years and 5 glacial-interglacial cycles (Spanish project “TORE5deglaciations”, CTM2017-84113-R, 2018-2020).

How to cite: Lebreiro, S. M., Nave, S., Antón, L., Michel, E., Kissel, C., Waelbroeck, C., McCave, N., Hodell, D., Flores, J.-A., Martinez-Ruiz, F., Martrat, B., Roque, C., Piotrowski, A., Skinner, L., Sierro, F., Terrinha, P., Cornen, G., Reguera, M. I., Lozano-Luz, R., and Bravo, N.: Drilling the Tore seamount- Archive of a natural oceanic sediment trap, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10110, https://doi.org/10.5194/egusphere-egu2020-10110, 2020.

EGU2020-2475 | Displays | SSP1.4

Evidence for polar surface-water incursions into the Gulf of Cadiz (SW Iberia) during the Early-to-Mid Pleistocene Transition

Aline Mega, Emilia Salgueiro, and Antje Helga Luise Voelker

The Mid Pleistocene Transition (MPT) was a global climatic event characterized by a drastic change in the deep thermohaline circulation during the glacial periods that resulted in more intense and longer lasting cold periods and cooler sea-surface temperature (SST). These changes might be linked to the atmospheric pCO2 reduction which in turn led to colder atmospheric temperatures and the expansion of continental ice sheets. In the mid-latitude North Atlantic, high-resolution records documenting the MPT's impact are still limited. Thus, this study's objective is to contribute to the knowledge by reconstructing circulation changes in the subtropical gyre realm off the southwestern Iberian Margin.  We use planktonic foraminifera faunal data from Integrated Ocean Drilling Program (IODP) Site U1387 (Faro Drift, Gulf of Cadiz) to characterize centennial-scale SST variations during the interval from Marine Isotope Stage (MIS) 18 to MIS 28. The results indicate relative stable SSTs during the interglacial and interstadial periods with temperatures around 20°C during summer and 16°C during winter. During MIS 20, 22, 24, and 25 short-termed extreme cold events were recorded when winter temperatures dropped below 5°C, during late MIS 22 even close to 0°C. They mark the terminal stadial events during deglaciation and were related to increased abundance of polar planktonic foraminifera species N. pachyderma that reached values near to 80%. N. pachyderma values. Percentages of that species between 90 and 50% can be found in the polar regions near the Arctic Front and those between 50 and 5% are indicative of subarctic waters. Whereas the terminal stadial events and the first stadial phase of MIS 22 were marked by incursions of polar surface waters to the southern Iberian margin, abrupt cold events during periods of continental ice shield growth of MIS 19, 21, 25 and 28 were associated with subarctic surface waters. During the MPT, the waters off southern Iberia, therefore, experienced cooling events more extreme than during the last glacial cycle.

How to cite: Mega, A., Salgueiro, E., and Voelker, A. H. L.: Evidence for polar surface-water incursions into the Gulf of Cadiz (SW Iberia) during the Early-to-Mid Pleistocene Transition, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2475, https://doi.org/10.5194/egusphere-egu2020-2475, 2020.

EGU2020-5452 | Displays | SSP1.4

Serpentinite mud volcanism and exhumation of fore arc- and lower plate material in the Mariana convergent margin system (IODP Expedition 366)

Walter Kurz, Irena Miladinova, Arianna V. Del Gaudio, Werner Piller, and Kurt Krenn

Serpentine seamounts located in the forearc region of a subduction zone setting represent an excellent natural laboratory for studying the geochemical processes acting along convergent plate margins and the associated natural hazards as well as the forearc structure and fault patterns. Active serpentinite mud volcanoes are currently restricted only to the Izu-Bonin-Mariana system, where old (presumably Cretaceous) oceanic lithosphere is subducting in the absence of an accretionary prism.

IODP Expedition 366 recovered cores from three serpentinite mud volcanoes at increasing distances from the Mariana trench (Yinazao, Fantangisña and Asùt Tesoru). Most of the material consists of serpentinite mud containing lithic clasts from the underlying forearc crust and mantle as well as from the subducting Pacific plate. A thin cover of pelagic sediments and volcanic ash deposits underlying the mud volcanos were also recovered. Recycled materials from the subducted slab are found at all three mud volcanoes and consist of metavolcanics rocks, metamorphosed pelagic sediments including cherty limestone as well as fault rocks.

Preliminary investigation of recovered sedimentary clasts from the summit of Fantangisña Seamount revealed that they contain primary calcite veins, whereas the latest veins are composed of aragonite (CaCO₃) and barite (BaSO₄).

Recovered clasts from the flank consist mainly of ultramafic rocks with various degrees of serpentinization. The serpentinite veins consist of lizardite and chrysotile, which suggests rather low temperatures of serpentinization (below 200 °C). Petrological analysis of metabasalt clasts from the same drilling hole shows changes in the mineral composition within the different intervals of the core. The composition of clinopyroxene varies between aegirine-augite and omphacite, but augite is also present. The presence of phengite with Si content of 3.5-3.8 a.p.f.u. indicates minimum pressure of 0.7 GPa at ~250 °C.

Furthermore, providing a detailed characterization of the fluids composition and transport would allow the better constraining of the tectonic and metamorphic history as well as the physical properties of the subducting Pacific Plate. Obtaining data on that point is in progress and will be presented additionally.

How to cite: Kurz, W., Miladinova, I., Del Gaudio, A. V., Piller, W., and Krenn, K.: Serpentinite mud volcanism and exhumation of fore arc- and lower plate material in the Mariana convergent margin system (IODP Expedition 366), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5452, https://doi.org/10.5194/egusphere-egu2020-5452, 2020.

The oceanographic cruise 89 (RRS James Cook) sailed in 2013 off the Iberian margin in support of an IODP proposal centred on IODP Site 1385. JC089 collected a range of hydrographic data and recovered a set of short sediment cores. We focus on 11 of the later, sampling the hydrography of the last c.400 years along a bathymetric gradient (600-4600 m). The stable isotopes (δ18O & δ13C) for: 8 common benthic foraminifer species with varied habitat preferences, the sediment pore-water and the bottom water above the sites were measured. The geochemical data is compared to various sedimentary and micropalaeontological data. The later comprises abundances of the main benthic foraminifera species >212μm, checking for living position of the endo-fauna in Rose-Bengal stained samples and for the abundances of phytodetritus-loving species E.exigua in the >90μm for all the 0-1cm samples. The study of the planktonic foraminifer assemblages along a gradient stretching 170 km offshore confirms the major influence of the upwelling to the East. Except for the epi-benthic species C.wuellestorfi, which records the bottom water δ13C at equilibrium, all other species failed to record the δ13C of the (pore) water at the depth of their living-position. We find that G.affinis could record the δ13CDIC near equilibrium with the pore-water at a depth of c.-1cm; therefore above its living population peak. This could be explained by vertical migrations through the sediment column at sites where the supply of organic matter is pulsed. The later assumption seems supported by a reverse correlation between high relative abundances of E.exigua and that of the planktonic upwelling indicator species G.bulloides under productivity pulses corresponding to higher Δδ13C(epi-G.affinis).

The Δδ13C varies from 1.7 to 4.9‰ (n=6) across a decreasing but increasingly pulsed surface productivity gradient further away from the coast. Across this range, G.affinis is observed living at increasing depths in the sediment but always peaks in oxic sediments. The absence of G.affinis from water deeper than 3100 meters prevents Δδ13C estimates at deeper water depths. For 6 of the 11 sites where G.affinis was present C.wuellestorfi occurred only twice. The δ13C for H.elegans and C.mundulus adjusted by -1.08 and +0.25‰ respectively (this study) were used instead for the shallower sites. Off the Iberian Margin the style of seasonally fluctuating food supply could be the main factor on Δδ13C. The implication on future and long-ranging IODP-based palaeoclimatic studies is that the Δδ13C could be used to estimate the type of productivity regime back in time. In the one hand the sites mostly influenced by the main upwelling cell exhibit Δδ13C < 3‰ & correspond to less than 10% of the time spent in an oligotrophic setting below 0.2mg (chla)/m3. In the other hand Δδ13C >3‰ trace offshore rare productive surface filaments in an environment otherwise corresponding to c.90% of the time under oligotrophic surface water. The absence G.affinis (for the range of depths studied) could indicate a record sitting outside either of these productive systems' influence.

How to cite: Mleneck-Vautravers, M. and Hodell, D.: Recent Foraminifers and Stable Isotopes Records on a Bathymetric Transect off Portugal (Cruise JC089) and implications for the Palaeoxygenation proxy, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7567, https://doi.org/10.5194/egusphere-egu2020-7567, 2020.

EGU2020-11898 | Displays | SSP1.4

Controls on stratigraphic variability in a semi-closed rift basin over the Late Quaternary, Gulf of Corinth, Greece

Sofia Pechlivanidou, Spyros Sergiou, Maria Geraga, Robert Gawthorpe, Dimitra Antoniou, Dimitra Angelopoulou, Mary Ford, and Natacha Fabregas

The Corinth Gulf is a semi-closed active rift basin, which alternated between marine and isolated/semi-isolated conditions as sea level fluctuated with respect to basin sills during Quaternary glacial/interglacial cycles. Results from the recent IODP Expedition 381 reveal cyclic variations of 10s-100s of kyr in sedimentation rates and basin paleoenvironment. In this study we investigate the controls on stratigraphic development of the Corinth basin during the last eustatic cycle and the Holocene based on core data from the IODP Expedition 381 Site M0079. We perform a multi-proxy analysis of the upper ~200 mbsf of core covering Marine Isotope Stages (MIS) 1-5 (i.e. last 130 kyr). Our analyses include grain size and micropaleontological (foraminifera) analyses at regular intervals (~0.5 m), Computed Tomography (CT-scanning) of selected u-channels and specific microscopic work (smear slides, SEM) on targeted samples. Our results show pronounced variability in sedimentation patterns during the isolated/semi-isolated phases compared to the marine intervals. Low density, thinly bedded and laminated muds alternating with high density homogenous mud beds and occasionally sandy, organic rich beds prevail during isolated/semi-isolated conditions. In contrast, homogenous and/or highly bioturbated successions characterize the marine sequences. The transitions from marine to isolated/semi-isolated conditions and vise-versa are often associated with authigenic carbonate deposition. Fine grained sediments (sand < 10%) dominate both the marine and the isolated sequences. Nevertheless, sandy turbidites (sand > 10%) are also present and are more often observed in the isolated phases, likely associated with climatic-driven changes in erosional processes onshore. Our analysis reveals short-lived isolated/semi-isolated sub-phases within the lower marine interval corresponding to the MIS5b and MIS5d lowstands. Short marine spikes also interrupt the isolated/semi-isolated conditions of the last glacial period indicating temporary sea level rises within MIS3. Overall, the marine intervals display significant paleoenvironmental differences although they share similar sedimentary patters. In particular, we observe more diverse palaeoceanographic conditions in the MIS5 marine sub-phases compared to the MIS1, especially regarding temperature and eutrophication levels of the water column.  

How to cite: Pechlivanidou, S., Sergiou, S., Geraga, M., Gawthorpe, R., Antoniou, D., Angelopoulou, D., Ford, M., and Fabregas, N.: Controls on stratigraphic variability in a semi-closed rift basin over the Late Quaternary, Gulf of Corinth, Greece, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11898, https://doi.org/10.5194/egusphere-egu2020-11898, 2020.

EGU2020-3407 | Displays | SSP1.4

Integration of drilling mud gas monitoring, downhole geophysical logging and drill core analysis identifies gas inflow zones in borehole COSC-1, Sweden

Simona Pierdominici, Thomas Wiersberg, Henning Lorenz, Bjarne Almqvist, and Iwona Klonowska and the COSC Science Team

The continuous wireline core drilling of the COSC-1 borehole (Jämtland, Central Sweden) offered the unique opportunity to combine data and findings from drilling mud gas monitoring, downhole geophysical logging and drill core analysis. The COSC project aims to better understand deep orogenic processes in mountain belts in a major mid-Paleozoic environment in western Scandinavia. The 2.5 km deep fully cored borehole COSC-1 was drilled in 2014 into the lower part of the Seve Nappe Complex, characterized by a thick sequence of high-grade metamorphic rocks. Here, we present results from a combination of drill mud gas monitoring with data from geophysical logging and core analysis to identify and characterize fluid-bearing open fractures during drilling of metamorphic rocks. Geophysical downhole logging is an established technique for extracting information from the underground. Online monitoring of drilling mud gas (OLGA) is also increasingly used in scientific drilling operations, but a combined interpretation of the data sets obtained with these methods has rarely been carried out in the past. Nearly complete gas records were obtained by OLGA with three meter depth resolution from 662 m to 1709 m and six meter resolution from 1709 m to 2490 m depth (COSC-1 total depth: 2496 m) for hydrogen, methane, carbon dioxide and helium by on-line drilling mud gas monitoring. Between 662 m and approx. 1550 m, both He and CH4 form broad peaks superimposed by several spike-like features. Zones with gas spikes coincide with high resistivity intervals identified by dual laterolog measurements and show fractures in optical drill core scans, borehole televiewer images, and visual core inspection. Therefore, we assume gas inflow through open fractures where deep/shallow resistivity ratios is greater than 1.5 imply the presence of free gas. The correlation between helium and deep/shallow resistivity ratios no longer appears at depths greater than 1550 m, probably because the formation gases are dissolved in formation fluids at higher pressure. 13 gas zones found in the depth interval 662 – 1550 m match with areas of higher resistivity and with open fractures identified by optical core logging. Below 1550 m depth, He drops significantly, whereas CH4 remains relatively high and H2 and CO2 reach maximum values. The high amount of hydrogen and methane at depths below 1616 m, from where friction between the casing and the drill string was reported, imply that these gases are most certainly artificially generated at depths below 1616 m and at least partly of artificial origin at shallower depths. Comparison between OLGA data and resistivity downhole logging data can help to estimate degassing depths: at depths where OLGA identified formation gases, concurrent high resistivity would be diagnostic for free gas, whereas low resistivity would imply gases dissolved in saline formation fluids.

How to cite: Pierdominici, S., Wiersberg, T., Lorenz, H., Almqvist, B., and Klonowska, I. and the COSC Science Team: Integration of drilling mud gas monitoring, downhole geophysical logging and drill core analysis identifies gas inflow zones in borehole COSC-1, Sweden, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3407, https://doi.org/10.5194/egusphere-egu2020-3407, 2020.

EGU2020-3891 | Displays | SSP1.4

Investigating glacial/interglacial cyclicity from downhole logging data and mineralogical composition: an example from the ICDP drilling project Lake Junín, Peru

Anja Schleicher, Simona Pierdominici, Christian Zeeden, Jochem Kück, Donald Rodbell, and Mark Abbott

Reconstructing the history of continental records covering the glacial-interglacial cycles was the main objective of the ICDP Lake Junín drilling project. Located at 4000 m above sea level, Lake Junín is characterized by a thick sediment package (>125 m) deposited with a sedimentation rate of 14-15 cm/kyr. In fact, the lake predates the maximum extent of glaciation, and is in a geomorphic position to record the waxing and waning of glaciers in the nearby Cordillera. Drilling was performed in 2015 at three sites and a suite of downhole logging measurements were applied. Downhole logging measurements were used to recognize the glacial and interglacial cycles, to reconstruct an age–depth model, to estimate sedimentation rates and to identify electrofacies. Initially, we investigate the consistency of cyclic sediment behavior and see that the interval from ~30-90 m shows a rather stable cyclicity with a wavelength of ~10 m. Natural and spectral gamma ray data were used for cyclostratigraphic analysis, and the astronomical spectral misfit (ASM) method was used to reconstruct the sedimentation rate. The results indicate a sedimentation rate of about 5-20 cm/kyr in the Lake Junín record. Furthermore, the TimeOpt method was applied to test for a fit of precession amplitude with eccentricity; it results in an average sedimentation rate of 15 cm/kyr. Both ASM and TimeOpt are astronomical testing approaches for untuned stratigraphic data in the depth domain that comprehensively evaluate a range of plausible time scales for the deposition history. This method suggests a good fit of the precession amplitude and an eccentricity filter when applying an average sedimentation rate of 14-15 cm/kyr. Based on these information on sedimentation rate, we establish a correlation of the spectral gamma ray data to the LR04 benthic isotope stack. In addition, the downhole logging data were used for cluster analysis to construct a lithological profile, called the electrofacies log.  Three major groups (carbonate-silt, peat and silt) have been identified by spectrum gamma ray, magnetic susceptibility, and p-wave velocity logs. With this method we are able to attribute the lithology in correspondence of core gaps. Finally, the properties of the clusters are analyzed and converted into lithological units according to the lithological information from the visual core description or mineralogical analysis or core material. To achieve this, 68 samples were taken in total from two core runs, in order to compare and characterize the minerals in the lake sediments at different depths. The mineralogical analyses performed by X-ray diffraction (XRD) show quartz, calcite, feldspar and clay minerals. The clay size fraction (< 2 micron) contains illite, smectite and kaolinite in different amounts. Linking the abundance and the lack of clay minerals in core samples with the downhole logging data, a relationship between geological history of the lake and climate change processes can be recognized. Consequently, the different mineralogical composition of the sediments, especially the presence or absence of smectite in the clay bulk, reflects a glacial/interglacial climate cyclicity.

How to cite: Schleicher, A., Pierdominici, S., Zeeden, C., Kück, J., Rodbell, D., and Abbott, M.: Investigating glacial/interglacial cyclicity from downhole logging data and mineralogical composition: an example from the ICDP drilling project Lake Junín, Peru, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3891, https://doi.org/10.5194/egusphere-egu2020-3891, 2020.

EGU2020-19628 | Displays | SSP1.4

Rock Magnetic and Magnetostratigraphic Study of Chicxulub Crater Impact Breccias and Post-Impact Carbonates in the Yaxcopoil-1 and Santa Elena Boreholes

Jaime Urrutia-Fucugauchi, Ligia Perez-Cruz, Elia Escobar-Sanchez, Miriam Velasco-Villarreal, and Edgar Garcia-Garnica

Chicxulub crater was formed ~66 Ma ago by an asteroid impact at the Cretaceous/Paleogene (K/Pg) boundary on the Yucatan carbonate platform in the southern Gulf of Mexico. The crater is the youngest and best preserved of the three large impact basins, with a ~200 km diameter and multi-ring and peak ring morphology. The crater, covered by post-impact carbonate sediments with thickness up to ~1.1 km, has been investigated by geophysical studies and drilling programs. Initial drilling in Yucatan was carried out by the Pemex oil company, followed by the National University UNAM Chicxulub program, the ICDP Yaxcopoil-1 project and the IODP-ICDP Expedition 364 marine drilling. Here, results of combined paleomagnetic, rock magnetic, petrographic and geochemical studies are used to characterize the sequence and constrain the unit’s emplacement and crater formation. We analyze core samples of suevitic breccias and Paleogene carbonates from the Yaxcopoil-1 and Santa Elena boreholes drilled in the southern sector, inside and to the south of the crater rim marked by the ring of cenotes.  Magnetic hysteresis, low-field susceptibility and coercitivity analyses indicate that main carriers are titanomagnetites and magnetite. Mineralogical and magnetic properties indicate effects of hydrothermal alteration, associated with the high temperature system generated by the impact. Higher coercitivity minerals are also observed in some samples. In the carbonate sections, hydrothermal effects as marked by the geochemical logs decrease upwards from the breccia-carbonate contact. Alternating field and thermal demagnetization is used to investigate the magnetization vector composition and isolate the characteristic remanent components. Magnetic polarities defined from the inclination data show a sequence of reverse to normal, which correlate to polarity chrons 29r to 26r, with impact occurring within 29r chron.  The correlations of the magnetostratigraphy and stable isotopes indicate a hiatus at the basal Paleocene section. In Santa Elena cores, d13C values range from 1.2 to 3.5%0 and d18O values range from -1.4 to -4.8%0, with variation trends correlating with the marine carbon and oxygen isotope records for the late Maastrichtian and early Paleocene. The positive carbon isotopes indicate high productivity after the K/Pg extinction event, while the oxygen isotope values are more negative reflecting regional and local effects. Silica contents decrease from high in the suevites to low values in carbonates showing higher variability and then increased contents at the Paleocene-Eocene Thermal Maximum (PETM). The geochemical trends correlate in other elements including iron, titanium, potassium and aluminum that record impact-induced hydrothermal effects and possibly changing depositional conditions. Ca shows an opposite trend, with lower values in the upper suevitic breccias, higher values in the Paleocene carbonates and lower values in the PETM.

How to cite: Urrutia-Fucugauchi, J., Perez-Cruz, L., Escobar-Sanchez, E., Velasco-Villarreal, M., and Garcia-Garnica, E.: Rock Magnetic and Magnetostratigraphic Study of Chicxulub Crater Impact Breccias and Post-Impact Carbonates in the Yaxcopoil-1 and Santa Elena Boreholes, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19628, https://doi.org/10.5194/egusphere-egu2020-19628, 2020.

Kerguelen Plateau (KP), one of the world’s largest Large Igneous Provinces, is located in a key region in the southern Indian Ocean. Its complex topography has a strong influence on pathways of water masses within the Antarctic Circumpolar Current (ACC) and the Antarctic Bottom Water (AABW). Thick sediment packages deposited on top and around KP are a high-fidelity recorders of significant modifications in pathways and intensities of water masses flowing across the KP during the Cenozoic. Already the previously ODP spot cored sedimentary sequences demonstrated their outstanding potential as a far-field monitor for the evolution of the Antarctic Ice Sheet, for the climate variability in the Warmhouse World of the middle to late Eocene, for changes in ocean circulation, and for migration of the Polar Frontal System. Here we propose to revisited KP and recover a complete, multiple-hole drilled, carbonate rich sedimentary successions from Labuan and Ragatt Basin area by an IODP Expedition. Only high-quality drilled, undisturbed new material will allow studying the interaction of climatic and tectonic changes of the last 66 million years and provide important information on the formation and dynamics of the Antarctic ice sheet due to the unique location of the KP.

How to cite: Westerhold, T. and Uenzelmann-Neben, G.: Kerguelen Plateau Drift Deposits: outstanding high-resolution chronicle of Cenozoic climatic and oceanographic changes in the southern Indian Ocean, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3121, https://doi.org/10.5194/egusphere-egu2020-3121, 2020.

EGU2020-3671 | Displays | SSP1.4

Detecting and using Milankovic cycles in borehole logging data: Comparing methods and application to Lake Ohrid

Thomas Wonik, Arne Ulfers, Matthias Sinnesael, Mingsong Li, and Christian Zeeden

Borehole logging data are not yet systematically assessed using cyclostratigraphic methods. In order to obtain a reliable understanding of (long) borehole logging datasets, and especially data from complex settings, a good understanding of the potential and specifics of relevant (time/depth) evolutive methods in cyclostratigraphy are an essential prerequisite. Therefore, we test a suite of evolutive cyclostratigraphic methods using several artificial datasets consisting of modelled Milankovic signals and noise.

Aim of this work is the comparison of different cyclostratigraphic methods for an understanding of which methods are suitable for Quaternary lake records, also for a good understanding of ICDP logging data. Once artificial datasets are discussed, we apply these methods to real data. A discussion of the possible issues and potential of especially uncommon methods gives insight in further potential of cyclostratigraphy.

Lake Ohrid is a tectonic lake located on the border of North Macedonia and Albania. With 1.36 Ma, it is considered Europe’s oldest lake and an important link between Mediterranean climate and African monsoon systems (Wagner et al. 2019). In 2013, an ICDP drilling campaign recovered 2100 m of sediments from four sites (Wagner et al. 2014).

Datasets from geophysical downhole logging provided by the Leibniz Institute for Applied Geophysics are used in a cyclostratigraphic analysis, which provides further insight into the sedimentation history of Lake Ohrid. Here we present initial results from the full succession in this sedimentary archive.

 

References:

Wagner, B., Wilke, T., Krastel, S., Zanchetta, G., Sulpizio, R., Reicherter, K., Leng, M. J., Grazhdani, A., Trajanovski, S., Francke, A., Lindhorst, K., Levkov, Z., Cvetkoska, A., Reed, J. M., Zhang, X., Lacey, J. H., Wonik, T., Baumgarten, H., and Vogel, H.: The SCOPSCO drilling project recovers more than 1.2 million years of history from Lake Ohrid. Sci. Dril., 17, 19–29, doi:10.5194/sd-17-19-2014 (2014).

Wagner, B., Vogel, H., Francke, A. et al.  Mediterranean winter rainfall in phase with African monsoons during the past 1.36 million years. Nature, 573, 256–260 (2019).

How to cite: Wonik, T., Ulfers, A., Sinnesael, M., Li, M., and Zeeden, C.: Detecting and using Milankovic cycles in borehole logging data: Comparing methods and application to Lake Ohrid, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3671, https://doi.org/10.5194/egusphere-egu2020-3671, 2020.

SSP1.5 – (Bio)mineral archives of past environmental conditions: from the Precambrian to the present

The formation of a solid-state material from solution is a ubiquitous process of fundamental importance not only for synthesis in solid-state chemistry but for a wide range of disciplines such as geosciences and biology. However, established classical crystallization theories fall short in explaining the outcome of crystallization and mineralization processes in complex environments, such as in biomineralizing organisms or geochemical and industrial settings.  The misfit between classical textbook knowledge and the plurality of conflicting experimental evidence facilitated the advent of an array of new crystallization concepts. These so-called nonclassical crystallization processes are fuelled by the attachment of multiatomic assemblies rather than by attachment of single ions drive crystal formation. Some of these models, such as oriented attachment, were unequivocally backed by experimental evidence and thus accepted by the science community. Other models have encountered distinct resistance from peers. At the centre of this intense dispute, we find the calcium carbonate system, which is of crucial importance for a range of disciplines. For this system, in particular, the existence of prenucleation clusters in the form of dynamically ordered liquid-like polyoxoanions (DOLLOP) has been suggested, and it has been claimed that nonclassical nucleation processes take place. However several groups have challenged this claim, claiming an entirely classical crystallization behaviour

Based on our results, we will draw a different picture of calcium carbonate formation. We show that the issues with this very systems root in its solute chemistry and the fact that this renders a calcium carbonate solution into a multicomponent system. We show liquid-liquid phase separation of near-neutral calcium carbonate solutions along with the first ultrastructural model of amorphous calcium carbonate (ACC). This findings give insight into the formation mechanisms of calcium carbonate under kinetically controlled conditions. Our findings further demonstrate that the formation of a liquid-condensed mineral precursor phase is not solely a “quirk of the peculiar calcium carbonate system” but a general phenomenon: it is an early stage precursor in the formation pathway of calcium carbonate under geo- and biochemical relevant conditions. Moreover, we show that this unexpected demixing behaviour is widespread, many inorganic components go through spinodal decomposition, when the reaction conditions are kinetically controlled and the solution chemistry disadvantage burst nucleation. Our data suggest that it is not the misconception and oversimplification of classical theories but our oversimplification of the solution chemistry which causes the current dispute on classical vs nonclassical nucleation of inorganic compounds. Currently, we see no need for invoking “non-classical” notions of nucleation since our exceptional observations can entirely be explained by established physicochemical concepts apart from CNT. Our results raise the awareness that a supramolecular solution and coordination chemistry provides the key to a thorough understanding of the genesis of inorganic solids under kinetically controlled conditions.

How to cite: Wolf, S.: From solutes to solids: towards a supramolecular view on mineralization processes, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21861, https://doi.org/10.5194/egusphere-egu2020-21861, 2020.

EGU2020-8680 | Displays | SSP1.5

Authigenic pyrite formation in iron-dominated marine sediments of the Mozambique Margin

Mark Zindorf, Jurjen Rooze, Christof Meile, Gwenael Jouet, Christian März, Robert Newton, Olivier Rouxel, Ewan Pelleter, Christophe Brandily, Nicolas Gayet, and Lucie Pastor

Sediment deposition along continental margins and especially close to the outlets of major river systems is highly dynamic and influenced by changing environmental conditions, such as sea-level variations and the shifting of ocean currents.
The upper slope of the Mozambique margin (SE Africa) receives its sediments from the Zambezi River and is the largest river-fed deposition center along the Eastern African Margin. Global sea level rise during the last glacial-Holocene transition led to a re-routing of the Zambezi River sediment plume. This caused order-of-magnitude changes in sedimentation rates along the shelf break of the Mozambique margin. The variable sediment input as well as changing organic matter load and quality resulted in non-steady state early diagenesis leading to changes in formation and upward flow of methane. This is reflected in temporally and spatially variable formation conditions of authigenic minerals (such as pyrite), especially at the sulfate-methane transition zone (SMTZ) where upward-diffusing methane is anaerobically oxidized by sulfate. Pyrite accumulations in sediment cores can be used to define the past positioning of SMTZs. The isotopic composition of sulfur in pyrite can provide information about the geochemical and environmental factors (e.g., availability of methane, sulfate, reactive iron) controlling the formation of these authigenic minerals during different times of sediment deposition.

We present geochemical data from sediment cores acquired in 2015 during the PAMELA-MOZ4 campaign onboard R/V Pourquoi Pas? offshore Mozambique. A reactive transport model is used to simulate the evolution of early diagenetic conditions over the time of sediment deposition (i.e., the last 27,000 years). By reproducing the currently observed mineral accumulations, the temporal development of methane generation and upward flux, and the past positioning of the SMTZ, can be reconstructed. With this, we are able to put a time constraint on past events of authigenic mineral accumulation and reveal their response to sedimentation rate changes caused by sea-level rise. We further discuss isotope signatures of small-scale diagenetic processes at the Mozambique margin.

This research was co-funded by TOTAL and IFREMER as part of the PAMELA scientific project.

How to cite: Zindorf, M., Rooze, J., Meile, C., Jouet, G., März, C., Newton, R., Rouxel, O., Pelleter, E., Brandily, C., Gayet, N., and Pastor, L.: Authigenic pyrite formation in iron-dominated marine sediments of the Mozambique Margin, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8680, https://doi.org/10.5194/egusphere-egu2020-8680, 2020.

EGU2020-2104 | Displays | SSP1.5

New insight into spheroidal iron (oxyhydr)oxide concretion formation models: Diagenetic concretion nucleation associated with neutral fluids from a mafic intrusion

Sally Potter-McIntyre, Justin Filiberto, Susanne Schwenzer, Jake Crandall, Scott Perl, and Bea Baharier

Directly west of the San Rafael Swell on the Colorado Plateau in the western U.S., the Jurassic Entrada Sandstone is intruded by a ~2 km long mafic dike. The dike is Miocene; however, the area is also crosscut by Laramide (~50Ma) clusters of deformation bands that are up 500 m long and up to ~3 m wide. The mafic intrusions infused the area with fluids that bleached the red sandstone directly surrounding the dike. On one side of the dike, the bleached area terminates at an adjacent deformation band set ~475 m south of the dike. Field observations suggest that the dike acted as a baffle preventing fluids from migrating further into the sandstone. Spheroidal calcite and iron (oxyhydr)oxide concretions are present in the bleached host rock, although calcite concretions (1-3 cm diameter) are present throughout the area on both sides of the deformation bands and in both red and white host rock. Iron (oxyhydr)oxide concretions (1-5 cm diameter) are limited to the uppermost bleached section between the dike and the deformation band set. Some iron concretions have solid interiors, and some have well-cemented rinds with interiors depleted of cement. Additionally, some iron concretions are nucleated on individual deformation bands that are ~2 mm wide and iron (oxyhydr)oxide cemented joint faces are also present. Thermochemical modeling shows the infiltrating Miocene fluids were CO2-bearing, but near neutral pH. The restricted location of the iron (oxyhydr)oxide concretions and relation to the calcite concretions suggest that stagnation of fluid is needed for spheroidal iron oxyhydroxide concretion formation. Calcite concretion nucleation and growth may be quicker resulting in more widespread occurrences, and/or may have preceded the Miocene fluids that infiltrated the unit. The evidence presented here shows that recently proposed models calling for calcite concretion precursors and acidic fluids for iron (oxyhydr)oxide concretion formation may not be correct.

How to cite: Potter-McIntyre, S., Filiberto, J., Schwenzer, S., Crandall, J., Perl, S., and Baharier, B.: New insight into spheroidal iron (oxyhydr)oxide concretion formation models: Diagenetic concretion nucleation associated with neutral fluids from a mafic intrusion, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2104, https://doi.org/10.5194/egusphere-egu2020-2104, 2020.

EGU2020-19949 | Displays | SSP1.5

Palygorskite in a Paleosol from Zagros mountain belt, NE Iraq

Axel Mentler, Polla Khanaqa, Kamal Karim, Franz Ottner, Jasmin Schomakers, Katharina Keiblinger, and Rosana Kral

In the semi-arid region south of Sulaimani city, paleosols can be found. The genesis of these paleosols needs to be elucidated. Here, we investigated a section of an Oligocene paleosol from that region. The section is about 7m thick with lower, middle and upper horizons, which consisted of partially weathered dolomitic limestone; conglomerate or lithified pebbly paleosol; and sandy-silty claystone or lithified clayey paleosol, respectively. These horizons were studied mineralogically and stratigraphically using X-ray diffraction, scanning electron microscopy, Simultaneous Thermal Analysis (STA) and granulometric analysis. Palygorskite content was higher in the conglomerate (lithified gravely paleosol) and in the partially weathered dolomitic limestone than in clayey paleosol.

Palygorskite is a trace mineral that allows to estimate climatic conditions during soil genesis. In hand specimen, palygorskite occurs as green patches of crystalline coating that covers pores and cavities on limestone and dolostone. Under scanning electron microscope, it appears as linear and fibrous loose bundles that occupy the interstice between the dolomite crystals and is mainly associated with dolostone and limestone facies.

We thus conclude that the climate was arid, and that the terrestrial land cover in this part of the Oligocene Basin in Northern Iraq was limestone and dolostone.

On this land, soil genesis and intermittent stream and sheet erosion was occurring during the entire Oligocene and it is well known, stratigraphically, as Oligocene Unconformity.

The possible origin of the palygorskite was the development during Oligocene by upward accumulation under hydrothermal condition in partially high weathered dolomitic limestone of Pila Spi formation during burial. Palygorskite occurs in marine, lacustrine and soil environments. Limited occurrences are associated with hydrothermal activity, in both marine and continental environments. Palygorskite-containing soils are limited almost exclusively to arid and semiarid areas of the world and are rather unstable in humid conditions.

The present paleosol was developed on Oligocene terrestrial land that bordered the sea covering Middle and Southern Iraq. Due to non-deposition weathering and mass wasting, calcareous gravely soil (limestone conglomerate) was generated. Sandy and clay soil were developed on the terrestrial land which stratigraphically formed an unconformity. This land was covered by water of a closed lagoon. Limestones are deposited as Lower Fars Formation.

These occurrences are associated with aquatic conditions characterized by alkaline solutions with high activities of Si and Mg. The most common setting for lacustrine palygorskite genesis are playa deposits, ancient lacustrine terraces, or closed-basin deposits of other types. While traces of palygorskite can be identified in a wide variety of soils, significant amounts of the pedogenically formed mineral are commonly associated with one specific situation of soil genesis like soils have been affected by fluctuating ground water, soil morphology that includes distinct and sharp textual transitions. This groups includes many paleosols. Most of these Paleosols are non-saline or only slightly saline.

How to cite: Mentler, A., Khanaqa, P., Karim, K., Ottner, F., Schomakers, J., Keiblinger, K., and Kral, R.: Palygorskite in a Paleosol from Zagros mountain belt, NE Iraq, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19949, https://doi.org/10.5194/egusphere-egu2020-19949, 2020.

EGU2020-11006 | Displays | SSP1.5

Laser-induced fluorescence (LiF) spectroscopy for detecting REE cross-contaminations in the Smithsonian rare-earth element phosphate standards

Margret C. Fuchs, Jan Beyer, Sandra Lorenz, Suchinder K. Sharma, Axel D. Renno, Johannes Heitmann, and Richard Gloaguen

Spectroscopy based methods have proven great potential in efficient, non-invasive material characterization. Recording the material-specific optical properties delivers instant information on the composition of an investigated sample surface without chemical sample preparation and may be operated in spatially continuous mode. In minerals, laser-induced fluorescence (LiF) provides a promising method to address the challenges of robust and efficient rare-earth element (REE) detection. The method is based on the characteristic electronic transitions within the incompletely filled f-shell of REE. The corresponding emission shows distinct features (spectral fingerprints) in the visible and near-infrared (VNIR) range of the electromagnetic spectrum that allow to distinguish between individual REE and mineral matrix luminescence. Only REE with completely filled or empty f-orbitals miss characteristic luminescence (i.e. Y3+, Sc3+, La3+, Lu3+), while the emissions of Gd3+ lie at lower wavelengths than the observed VNIR range.

We test the suitability of LiF in applications of REE identification by (1) building a spectral LiF library from a sample set of luminescent REE phosphates and (2) evaluating observed emissions in samples of non-luminescent REE, and (3) comparing indicated REE cross-contamination to results of neutron activation analysis (NAA). As samples, we use the Smithsonian REE phosphate standards for electron microprobe analysis. The synthetic material delivers a simple, well-defined host composition, is well investigated and NAA results are available on additional trace REE concentration resulting from the material production procedure. The trace REE concentrations are at the order of 10-4 given in mass fraction. We employ laser-induced fluorescence at three commonly used laser wavelengths (325 nm, 442 nm, 532 nm) to acquire our REE sample spectra and record LiF signals in the visible to near-infrared spectral range (350 – 1080 nm).

The comparison of spectra from non-luminescent REE phosphates shows clear similarities in emission patterns that can be assigned to specific luminescent REE using the spectral LiF library. Our results demonstrate the suitability of LIF for REE detection along with the benefits of selective element excitation and highlight the high sensitivity of the LiF method. The detected emissions in the non-luminescent samples indicate a detection limit below mass fractions of 10-4, when compared to NAA results, but also show that not all REE are equally responsive. Here, the co-existence of REE with complex interactions such as charge transfer contributes to the observed emission pattern. Adding to the spectral LiF library data and expanding investigations to further mineral hosts will facilitate new applications of LIF for REE analysis in natural samples and its implementation in raw material exploration.

How to cite: Fuchs, M. C., Beyer, J., Lorenz, S., Sharma, S. K., Renno, A. D., Heitmann, J., and Gloaguen, R.: Laser-induced fluorescence (LiF) spectroscopy for detecting REE cross-contaminations in the Smithsonian rare-earth element phosphate standards , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11006, https://doi.org/10.5194/egusphere-egu2020-11006, 2020.

The diameter of framboidal pyrites was widely used as a measure of redox condition in modern and ancient sedimentary environments, the proposed critical values of average size and standard deviation of framboids are about 8μm and 3μm respectively. However, a few reports proposed that the exceptionally large size and standard deviation of framboidal pyrites in cored sediments from northeastern South China Sea is closely related to the anaerobic oxidation of methane (AOM) processes mainly dominated in sulfate-methane transition zones (SMTZ). Here we investigate the occurrence of framboidal pyrites in two cored sediments of sites SC-W02B-2017 and SC-W03B-2017 at Shenhu area during the first offshore gas hydrate production test in northern South China Sea. Combined with the statistics of size and standard deviation of framboidal pyrites, the relative concentrations and sulfur isotopic compositions of bulk pyrites, we verified that the AOM could enhance the framboidal pyrite formation. Our data show that both the size and the standard deviation of framboidal pyrite present an unusual positive excursion in cored sediment column. By interpreting the coupling occurrence of positive excursions both pyrite concentrations and sulfur isotopes, four main paleo-sulfate-methane transition zones (Paleo-SMTZ) are roughly recognized in depths around 50 meter below seafloor (mbsf), 90-100 mbsf, 135-225 mbsf and 180 mbsf, where unusual strong AOM and unusual methane releases might happened. The morphology shows most of the pyrite framboids occur in framboidal cluster with a rod-like, irregular block shape and secondary overgrowth. The size of pyrite framboids in site W02B ranges from 8.1μm to 40.1μm with maximal about 40.1μm and in site W03B from 8.6μm to 25.3μm with maximal about 101.2μm (n=2686 from 13 samples). Our data show the average size and the standard deviation of pyrite framboids are more than 20μm and 3.0μm respectively, and the higher δ34S value and larger size of framboid mainly occur near the intervals of paleo-SMTZs in marine sediment columns. Therefore, we propose again that the enhancing AOM in SMTZs could flourish the growth of pyrite framboids and enlarge the standard deviation of framboidal size, which might be implication for more precise interpretation of redox condition of sedimentary environments using framboidal pyrite diameter.

How to cite: Wang, J. and Wei, Q.: Framboidal pyrites flourished in sulfate-methane transition zones of cored sediments in the northern South China Sea, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3979, https://doi.org/10.5194/egusphere-egu2020-3979, 2020.

EGU2020-15902 | Displays | SSP1.5

Building amorphous calcium carbonate into geochemical biomineralisation models

David Evans, William Gray, James Rae, Rosanna Greenop, Paul Webb, Kirsty Penkman, Roland Kröger, and Nicola Allison

Amorphous calcium carbonate (ACC) has been observed, or inferred to exist, in the majority of the major phyla of marine calcifying organisms. The CaCO3 produced by these organisms represents one of the largest long-term carbon sinks on Earth’s surface, such that identifying how calcification will respond to anthropogenic climate change is an urgent priority. A substantial portion of our knowledge of the biomineralisation process of these organisms is derived from inferences based on skeletal geochemical data, yet such models typically do not include an ACC component because little is known about trace element and isotope fractionation into ACC. In order to address this, we present, to our knowledge, the first structural and geochemical data of ACC precipitated from seawater under varying carbonate system conditions, seawater Mg/Ca ratios, and in the presence of three of the most common intracrystalline amino acids (aspartic acid, glutamic acid, and glycine). Based on these data we identify the carbonate system conditions necessary to produce ACC from seawater [Evans et al., 2019], and identify the dominant controls on ACC geochemistry. As an example, we utilise these data to build a simple biomineralisation model for the low-Mg (e.g. planktonic) foraminifera, based on precipitation of low-Mg calcite through an ACC precursor phase in a semi-enclosed pool. This exercise demonstrates that the observed shell geochemistry of this group of organisms can be fully reconciled with a model that includes an ACC component, and moreover that constraints can be placed on the degree of ACC utilisation and the ACC-calcite transformation process. More broadly, the exercise demonstrates that knowledge of the characteristics and geochemistry of ACC is important in the development of a process-based understanding of marine calcification.

Evans, D., Webb, P., Penkman, K. Kröger, R., & Allison, N. [2019] The Characteristics and Biological Relevance of Inorganic Amorphous Calcium Carbonate (ACC) Precipitated from Seawater. Crystal Growth & Design 19: 4300.

How to cite: Evans, D., Gray, W., Rae, J., Greenop, R., Webb, P., Penkman, K., Kröger, R., and Allison, N.: Building amorphous calcium carbonate into geochemical biomineralisation models, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-15902, https://doi.org/10.5194/egusphere-egu2020-15902, 2020.

EGU2020-19690 | Displays | SSP1.5 | Highlight

Microbial control on Anthropocene carbonates in slag drainage waters

Cees van der Land, Keziah Cowan, Angela Sherry, Laura Bastianini, Neil Gray, Mike Rogerson, Ramon Mercedes-Martin, Timothy Prior, Edgley Cesar, and William Mayes

Over the last decennia, alkaline leachates from the weathering of legacy steel slag disposal sites have affected the surrounding soils and drainage streams. The hyperalkaline and hypersaline conditions around these sites are comparable to extreme paleo environments such as alkaline lakes in rift volcanic settings. Investigating the carbonate deposits forming in these man-made systems provides a unique opportunity to link the ongoing physical and microbial processes to their resultant carbonate morphologies.

Here we present data from 3 sites across Dene Burn, a slag drainage stream in Consett, County Durham, UK. After 100 years, iron and steel production ceased in 1980, leaving over 20 million tons of slag in the form of several large mounds. Analysis showed Dene Burn to be typical of slag drainage waters with an elevated pH (>9) and saturated with different secondary phase minerals- particularly calcite. However, the physical distribution of carbonates is more comparable with estimated local kinetic precipitation rate than it is to thermodynamic saturation, indicating that the fundamental control on carbonate formation arises from crystal surface processes. A microbial community comprising predominantly Proteobacteria (Alpha-, Gamma-, Beta- and Deltaproteobacteria), Cyanobacteria, Bacillariophyta (diatoms) and Bacteroidetes (Flavobacterium) was identified at the 3 sites. The microbial communities and an abundance of extracellular polymeric substances (EPS) were shown in close association with the mineral phases detected at the sites. The presence and composition of these biofilms appears to control local carbonate mineralisation rates and carbonate morphologies.

Drainage streams from steel slag provide a unique opportunity to study carbonate mineral formation under extreme environmental conditions. Furthermore, maximising carbonate formation at such sites could be utilised as a remediation and carbonate sequestration technique.

How to cite: van der Land, C., Cowan, K., Sherry, A., Bastianini, L., Gray, N., Rogerson, M., Mercedes-Martin, R., Prior, T., Cesar, E., and Mayes, W.: Microbial control on Anthropocene carbonates in slag drainage waters, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19690, https://doi.org/10.5194/egusphere-egu2020-19690, 2020.

EGU2020-20253 | Displays | SSP1.5

Biogeohemical significance of Intracellular calcification by Cyanobacteria

Neha Mehta, Feriel-Skouri Panet, and Karim Benzerara

Cyanobacteria are an abundant and diverse group of photosynthetic bacteria that have shaped Earth’s environment for billions of years and play a vital role in the cycling of numerous elements such as carbon, calcium, and phosphorus. In particular, their impact on the global carbon cycle is of significant interest in the context of carbon capture and climate change, as they sequester atmospheric CO2 into organic carbon and biogenic calcium carbonates (CaCO3) through a process called calcification.  The process of calcification has long been considered as extracellular and non-biologically controlled. However, recently, several cyanobacterial species have been reported to form intracellular amorphous calcium carbonate (ACC) inclusions. These cyanobacteria were found in diverse environments and accumulate high concentrations of AEE (Ca, Ba and Sr) from solutions undersaturated with respect to AEE-carbonate phases. Moreover, one of these cyanobacteria species, G. lithophora was shown to selectively accumulate stable and radioactive alkaline earth elements (AEE) within the intracellular amorphous carbonates and/or polyp inclusions (Mehta et al., 2019). Recently, it was confirmed that cyanobacteria forming intracellular ACC contained a much higher content of alkaline earth elements (AEE) than all other cyanobacteria (DeWever et al., 2019). The high concentration of Ba and Sr within these intracellular inclusions was surprising because Ba and Sr have usually been considered as having no physiological role at all. The high concentration of Ca within these intracellular inclusions was directly in contrast with the traditional paradigm of cells maintaining a state of homeostasis with respect to Ca. Furthermore, Sr/Ca and Ba/Ca ratios in these ACC inclusions were very different from those expected from abiotic precipitation in the solution surrounding the cells (Cam et al. 2015). To understand the biological driver behind these observations, first, I will present a review of the above mentioned “vital effects” in the context of intracellular calcification in cyanobacteria. Second, using batch incubation experiments, I will show that high Ca concentrations are vital not only for the growth of G. lithophora, but also for the uptake of Ba by G. lithophora. Lastly, I will examine Ca homeostasis in ACC forming cyanobacterial strains by using an antagonist/inhibitor of a known channel/transporter involved in Ca transport.  Overall, these insights will shed some light on the role of cyanobacteria forming intracellular ACC on carbonate (bio)mineralization, in both modern and ancient Earth’s environment. 

Reference:

N Mehta, K Benzerara, B Kocar, V Chapon, Sequestration of radionuclidesRadium-226 and Strontium-90 by cyanobacteria forming intracellular calcium carbonates, ES&T 2019

De Wever, A.; Benzerara, K. et al. Evidence of High Ca Uptake by Cyanobacteria Forming Intracellular CaCO 3 and Impact on Their Growth. Geobiology 2019

Cam, N., Georgelin, T., Jaber, M., Lambert, J.-F., and Benzerara, K, In vitro synthesis of amorphous Mg-, Ca-, Sr- and Ba-carbonates: what do we learn about intracellular calcification by cyanobacteria? Geochim. Cosmochim. Acta 2015

 

How to cite: Mehta, N., Panet, F.-S., and Benzerara, K.: Biogeohemical significance of Intracellular calcification by Cyanobacteria, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20253, https://doi.org/10.5194/egusphere-egu2020-20253, 2020.

EGU2020-21988 | Displays | SSP1.5 | Highlight

Boron proxies and biomineralisation: the possible, the impossible and the likely.

Oscar Branson and Alex Gagnon

The abundance and isotopic content of boron in carbonate biominerals provide our best records of ocean carbon chemistry and pH, which have proved instrumental in studying past episodes of CO2-induced climate change. The boron proxies are based on the theory that carbonates solely incorporate B(OH)4- in proportion to seawater B(OH)4-/HCO3- or B(OH)4-/CO32-, capturing both the state of the ocean C system and the pH-dependent isotopic composition of B(OH)4-. However, models of biomineralisation invoke significant modification of internal carbon chemistry to facilitate calcification, and substantial proton export has been observed during carbonate formation. The pH, carbon and boron chemistry at the site of calcification cannot be the same as that of external seawater. How, then, do biominerals appear to record seawater B(OH)4-? While unanswered, this question raises serious problems for our interpretation and use of the B proxies.

We explore this question using a quantitative model of B transport and incorporation in biomineralisation. Three key fluxes dominate biomineral formation: CaCO3 precipitation, the exchange of seawater with the external environment, and ion transport across membranes by diffusion or active pumping. By reducing the problem to the balance between these three key fluxes, it is possible to explore a wide range of biomineralisation scenarios with minimally restrictive assumptions. Within this framework, we consider both the transport of B(OH)4-, and the transport and passive diffusion of membrane-permeable B(OH)3, allowing us to explore a comprehensive range of candidate biomineralisation scenarios and B transport processes.

By explicitly including the independent transport of both B species, our model offers two key insights into the mechanisms behind the boron proxies and biomineralisation:

  1. We identify biomineralisation mechanisms that allow B geochemistry to record external seawater conditions, despite the modified chemistry at the calcification site.

  2. We constrain the dynamics of the calcification environment (e.g. ‘closed’ vs. ‘open’ or Rayleigh- vs. transport-dominated system) by inverting the model to consider paired B/Ca and δ11B data, offering key new constraints on ion transport processes in biomineralisation.

How to cite: Branson, O. and Gagnon, A.: Boron proxies and biomineralisation: the possible, the impossible and the likely., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21988, https://doi.org/10.5194/egusphere-egu2020-21988, 2020.

EGU2020-19994 | Displays | SSP1.5

δ11B and B/Ca ontogenetic variability within Globigerina bulloides

Matthieu Buisson, Pascale Louvat, Szabina Karancz, Ruchen Tian, Markus Raitzsch, Jelle Bijma, and Claire Rollion-Bard

Understanding the atmosphere-continent-ocean carbon cycle and its associated oceanic carbon system is one of the keystones to face the Anthropocene’s climate change. Since the 1990s the isotopic ratio of boron (δ11B) in calcitic shells of planktonic foraminifera has proven to be a powerful geochemical proxy to determine the oceanic paleo-pH and its link to atmospheric CO2 level over geological times1, whereas the ratio B/Ca as proxy of the seawater carbonate chemistry is still questionable2,3.

However, the use of planktonic foraminifera in paleoclimatic reconstructions requires calibrations of the pH – δ11B relationships to correct what is known as « vital effect »4: each species controls differently its calcification process and consequently slightly modifies the seawater chemistry during biomineralization5,6. Moreover, shell size effect on δ11B has been reported for some symbiont-bearing species due to photosynthetic increase of pH7,8.

Calibrations for the symbiont-barren Globigerina bulloides have been already determined9,10 but sparse data have been reported so far for the test size effect on δ11B 11.

Here we measured the δ11B of three different fractions (250-315, 315-400 and >400 μm) of G. bulloides sampled along the coretop PS97-122 from the Chilean margin (54.10°S, 74.91°W), by using a new protocol developed at IPGP and dedicated to small samples which couple a microsublimation technique and a micro-direct injection device (μ-dDIHEN12). Our preliminary results show significantly higher δ11B values for the large fractions compared to the small ones, as found for symbiont-bearing planktonic species such as Globigerinoides sacculifer7 and Globigerinoides ruber8.

 

  • (1) Pearson & Palmer, 2000, Nature 406, 695-699
  • (2) Yu et al., 2007, Paleoceanography 22, PA2202
  • (3) Allen et al., 2012, EPSL 351-352, 270-280
  • (4) Urey et al., 1951, Soc. Am. Bull. 62, 399-416
  • (5) Erez, 2003, Rev. in Min. and Geochem. 54 (1), 115-149
  • (6) de Nooijer et al., 2014, Earth-Science Reviews 135, 48-58
  • (7) Hönisch & Hemming, 2004, Paleoceanography 19, PA4010
  • (8) Henehan et al., 2013, EPSL 364, 111-122
  • (9) Martínez-Botíet al., 2015, Nature 518, 219-222
  • (10) Raitzsch et al., 2018, EPSL 487, 138-150
  • (11) Henehan et al., 2016, EPSL 454, 282-292
  • (12) Louvat et al., 2019, JAAS 8, 1553-1563

How to cite: Buisson, M., Louvat, P., Karancz, S., Tian, R., Raitzsch, M., Bijma, J., and Rollion-Bard, C.: δ11B and B/Ca ontogenetic variability within Globigerina bulloides , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19994, https://doi.org/10.5194/egusphere-egu2020-19994, 2020.

Despite being some of the largest bio-constructions on the planet, coral reefs are made by many millions of cm- to mm-sized polyps of Scleractinian corals. Calcification occurs in a micron sized space sandwiched between the coral animal and the existing skeleton, known as the extra cellular medium (ECM). The coral animal has a tight control on the carbonate system in this space through deploying enzymatic pumps (e.g. Ca-ATPase) and secreting acidic-rich proteins. Tracking the state of the carbonate system in the ECM is therefore key to forming a mechanistic understanding of how environmental change, such as ocean acidification, influences skeletal formation and ultimately the growth and resilience of these important ecosystems.

Traditional means to examine ECM composition is through the use of micro-electrodes. While these approaches have revealed many key insights they are, by their nature, invasive.  They also only provide snap shots of information for corals grown in the laboratory. The boron isotopic composition of the coral skeleton and its boron content (expressed as B/Ca ratio) have recently emerged as a viable alternative approach to fully characterise the carbonate system in the ECM.  However, most studies employ bulk sampling techniques which require averaging across both structural elements of the coral skeleton and many months to years of growth. Laser ablation MC-ICP-MS approaches are now available as an alternative sampling protocol (e.g. Standish et al. 2019), and along with B/Ca (and other trace element) measurements this not only allows a reconstruction of the full carbonate system of the ECM from an analysis of the skeleton of any coral (cultured or wild) at unprecedented spatial and temporal resolution, but it also allows an examination of the influence of the carbonate system in the ECM on trace element incorporation. 

Here we present boron isotope and trace element analyses of several tropical, reef-building, corals to examine the nature and magnitude of fine scale variation in ECM composition.  By studying corals from locations where external seawater is well known we also gain insights into trace element incorporation and whether external seawater pH can be accurately reconstructed from the boron-based proxies at weekly (or better) resolution. 

 

Standish, C.D., Chalk, T.B., Babila, T.L., Milton, J.A., Palmer, M.R., Foster, G.L. (2019) The effect of matrix interferences in situ boron isotope analysis by laser ablation MC-ICP-MS, Rapid Communications in Mass Spectrometry 33: 959–968 https://doi.org/10.1002/rcm.8432

How to cite: Foster, G. L., Chalk, T. B., and Standish, C. D.: Boron isotope analysis of coral skeletons by laser ablation MC-ICP-MS: new insights into calcification and environmental reconstruction at high temporal resolution , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8202, https://doi.org/10.5194/egusphere-egu2020-8202, 2020.

A widespread phenomenon in biogenic and inorganic carbonates that are formed out of isotopic equilibrium is a nearly ubiquitous co-variation (slope) of carbon vs. oxygen isotopes, in e.g., speleothem and cryogenic carbonates, shells and skeletons of foraminifera, corals etc. For proxy calibrations, it is critical to understand such isotope variations (often labeled kinetic or vital effects) in proxies widely used for paleo-reconstructions. Given that this phenomenon is observed in inorganic carbonates and biogenic carbonates across different phyla suggest a common underlying mechanism, possibly independent of biological controls, that is, likely of inorganic origin. Here we present results from laboratory experiments on synthetic carbonate precipitation to constrain the kinetic isotope fractionation factor (KFF) of carbon and oxygen during CO2 hydration. We used an experimental setup similar to that of an earlier study but with important modifications and tight temperature and pH control. The average d13C and d18O values of our carbonate samples (BaCO3) produced at 25 deg C and pH = 8.0 (NBS) are -29.7 +- 0.71 per mil (VPDB) and 18.8 +- 0.56 per mil (VSMOW), respectively. From the isotope data, we calculate our experimental 13KFF and 18KFF, which refer to the 13C/12C and 18O/16O fractionation between CO2(g) and BaCO3, where the d13C and d18O values of CO2(g) were calculated using known equilibrium fractionation factors. Our results show that our KFFs are the largest values compared to previously reported experimental KFFs (except for one study), suggesting that our values are closest to the full isotopic disequilibrium during CO2 hydration. Based on our KFFs, we will present the expected slope of carbon vs. oxygen isotopic disequilibrium from kinetic effects during CO2 hydration. We will also discuss the expected slope from equilibrium effects of solution pH on oxygen isotopes. Comparison with field and culture data will reveal the origin of the slope of carbon vs. oxygen isotopic disequilibrium in biogenic and inorganic carbonates.

How to cite: Zeebe, R., Yumol, L., and Uchikawa, J.: Solution to an enigma: Explaining the slope of carbon vs. oxygen isotopic disequilibrium in biogenic and inorganic carbonates, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10573, https://doi.org/10.5194/egusphere-egu2020-10573, 2020.

EGU2020-3051 | Displays | SSP1.5

Combined clumped isotope measurements resolve kinetic biases in carbonate formation temperatures

David Bajnai, Weifu Guo, Niklas Löffler, Katharina Methner, Emilija Krsnik, Tyler B. Coplen, Eberhard Gischler, Maximilian Hansen, Daniela Henkel, Gregory D. Price, Jacek Raddatz, Denis Scholz, and Jens Fiebig

Reaction kinetics involved in the precipitation of carbonates can introduce large scatter and inaccuracies in the temperatures derived from their δ18O and ∆47 values. Advances in mass spectrometry instrumentation recently enabled high-precision analysis of the 18O–18O clumping in carbonate minerals (48), despite the relatively low natural abundance of 12C18O18O, the main isotopologue contributing to the 48 signal (1). Measurements of 48, when combined with 47, can yield additional insights into kinetic effects and the carbonate formation environment (2).

Here we report high-precision 47 and 48 values of speleothem carbonates, modern coral skeletons, a brachiopod, and a belemnite. We constrained equilibrium in 47 vs 48 space by anchoring empirically derived 47 vs temperature and 48 vs temperature relationships to a Devils Hole mammillary calcite, known to be precipitated at extremely slow rates at a constant 33.7(±0.8) °C and water oxygen isotope composition. Our results, compared to theoretical predictions, provide the most substantial evidence to date that the isotopic disequilibrium commonly observed in speleothems and scleractinian coral skeletons is inherited from the dissolved inorganic carbon pool of their parent solutions. Data from an ancient belemnite imply it precipitated near isotopic equilibrium and confirm the warmer-than-present temperatures at Early Cretaceous southern high latitudes. The presence of similar kinetic departure in a brachiopod but not in a belemnite suggests that the current discrepancy between belemnite and brachiopod-based temperature estimates in the geologic record is most likely related to a greater kinetic bias in the isotopic composition of brachiopod shells.

We demonstrate that the combined clumped isotope method makes it possible to identify carbonates that did not precipitate in thermodynamic equilibrium from their parent water. Our results highlight the potential that the combined clumped isotope analyses hold for accurate paleoclimate reconstructions and the identification of the kinetic fractionation processes dominant in carbonate (bio)mineralisation.

(1) Fiebig et al. (2019), https://doi.org/10.1016/j.chemgeo.2019.05.019

(2) Guo, W. (2020), https://doi.org/10.1016/j.gca.2019.07.055

How to cite: Bajnai, D., Guo, W., Löffler, N., Methner, K., Krsnik, E., Coplen, T. B., Gischler, E., Hansen, M., Henkel, D., Price, G. D., Raddatz, J., Scholz, D., and Fiebig, J.: Combined clumped isotope measurements resolve kinetic biases in carbonate formation temperatures, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3051, https://doi.org/10.5194/egusphere-egu2020-3051, 2020.

The Mg/Ca paleotemperature proxy in planktic foraminifera is one of the most widely-used proxies for sea surface temperature. However, this ratio is not constant throughout the test, varying systematically by several fold independent of temperature between faster and slower growing diurnal bands. This phenomenon has yet to be explained mechanistically, however, changing calcification rates may be a contributing factor. Observing the relationship between calcification rate and trace metal incorporation for multiple proxies at the scale of this banding will allow us to better understand the contribution of kinetic effects to heterogeneity. In this study, we examine Me/Ca ratios on a diurnal cycle in Orbulina universa, utilizing a novel approach based on multiple isotopic spikes that allows us to measure Sr/Ca, Li/Ca and Mg/Ca with the precision of isotope dilution while still maintaining the time resolution of microanalytical techniques. Using independently measured growth rates derived from NanoSIMS measurements of diurnal Mg/Ca heterogeneity, we examine the effect of crystal growth rate on foraminiferal Sr/Ca and Li/Ca.  We observe that Sr/Ca ratios in foraminifera are ~3% higher during the night than during the day, which initially appears opposite to the expected signal based on growth rate. However, we also observe a positive correlation between Sr and Mg in foraminiferal calcite, which falls on the same mineralogical line as the Sr/Ca and Mg/Ca of other biogenic and inorganic calcites. We attribute offsets in calcite composition from this mineralogical relationship to kinetics. Interpreted within that framework, day Sr/Ca ratios appear more affected by kinetics than night Sr/Ca ratios, which is consistent with observed calcification rates. The difference between any given data point and the mineralogical line can be explained by kinetic processes, and correlates with oceanographic properties in cultured foraminifera, which could help separate temperature from growth rate effects in the paleorecord.

How to cite: Bonnin, E., Spero, H., and Gagnon, A.: Testing the effect of crystal growth rate on foraminiferal calcite microchemistry using Sr/Ca of individual day/night bands, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13960, https://doi.org/10.5194/egusphere-egu2020-13960, 2020.

EGU2020-7573 | Displays | SSP1.5

Exploring the biomineral morphology of crossed-lamellar bivalve shells as a water temperature proxy

Nils Höche, Melita Peharda, Julien Thébault, and Bernd R. Schöne

Bivalve shells serve as excellent high-resolution archives of marine paleoclimate. Recently, ultrastructural features of the shells were investigated as potential temperature proxies that can overcome the limitations of the stable oxygen isotope method (i.e., missing data on past seawater oxygen isotope signature and diagenetic overprint). According to previous studies, the size of individual biomineral units of prismatic, nacreous and crossed-lamellar ultrastructures in cross-sections along the axis of maximum growth was solely related to water temperature. Despite being present in 90% of all mollusks, the crossed-lamellar ultrastructure was only studied for environmental relationships in one species (Glycymeris bimaculata) until now. To determine whether this new proxy can be applied to other bivalves with crossed-lamellar ultrastructure, further studies are needed.

We analyzed the shells of other Glycymerididae collected at near-shore and shelf environments (G. nummaria and G. pilosa: Adriatic Sea, Croatia; G. glycymeris: Iroise Sea, France; Glycymeris sp: Southern Pacific, New Zealand) by means of SEM, using a previously developed automatic image analysis procedure. Morphological changes of the biomineral units of the shells were assessed for relationships with temperature, salinity and food availability. Additionally, the crossed-lamellar architectures of phylogenetically more distantly related taxa (Venus verrucosa and Callista chione: Adriatic Sea, Croatia) were assessed.

Our results show that all studied Glycymerididae species, irrespective of environmental setting and locality, formed larger biomineral units in warmer waters. However, biomineral properties of ontogenetically old shell portions are more difficult to interpret, because declining growth rates condense the shell record and aggravate ultrastructural analyses. The crossed-lamellar shell layers of V. verrucosa and C. chione exhibited hierarchical organizations very similar to those of the Glycymerididae. The ultrastructural temperature proxy can therefore be applied to crossed-lamellar shells of bivalves from a wide range of coastal settings, preferably in ontogenetically young shell portions.

How to cite: Höche, N., Peharda, M., Thébault, J., and Schöne, B. R.: Exploring the biomineral morphology of crossed-lamellar bivalve shells as a water temperature proxy, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7573, https://doi.org/10.5194/egusphere-egu2020-7573, 2020.

EGU2020-4724 | Displays | SSP1.5

Ba/Ca, P/Ca, Li/Ca and Mn/Ca ratios in the deep-sea bivalve Acesta excavata: Valuable tools to reconstruct plankton dynamics in cold-water coral ecosystems?

Nicolai Schleinkofer, Jacek Raddatz, David Evans, Axel Gerdes, Silke Voigt, and Max Wisshak

Phytoplankton is one of the most important producers of oxygen, and plays an important role in the export of large amounts of carbon to the deeper ocean. Since phytoplankton is also the basis of most food webs in the ocean, understanding the dynamic system of phytoplankton is a crucial part to understand past carbon- and nutrient cycles and paleoclimatic changes. The export of nutrients is also an important factor impacting cold-water coral (CWC) reefs and may play a role in controlling their distribution. Here we present laser ablation inductively coupled mass spectrometer (LA-ICP-MS) Element/Ca measurements from Acesta excavata, a file clam, often associated with cold-water coral reefs along the European continental margin. Environmental parameters were recorded with lander systems directly deployed in the CWC reefs, which allows us to compare our geochemical data to in-situ ocean data.

Our results reveal, that Ba/Ca ratios show stable baseline values with intermittent sharp peaks. The location of these peaks in between major growth lines and temperature reconstructions with Mg/Sr ratios (Schleinkofer et al., submitted) show that these peaks occur during Winter and are repeatable between samples from the same location. This indicates a strong external forcing mechanism and allows cross-dating of different bivalve shells. While the occurrence of Ba/Ca peaks correlates with phytoplankton maxima, the absolute Ba/Ca ratio does not correlate with the phytoplankton abundance.

Mn/Ca ratios show similar trends as Ba/Ca ratios but the peaks are phase shifted and occur slightly delayed. These peaks could be triggered by decreasing oxygen concentrations in the water caused by the decomposition of organic material.

As A. excavata does not show easily distinguishable growth lines under the light microscope despite of Mutvei staining or fluorescence microscopy, we hypothesize that P/Ca ratios might be usable to locate highly phosphorylated shell areas that usually correlate with major growth lines. P/Ca ratios show no perceivable features in the vicinity of major growth lines. Instead we recognize that Ba/Ca peaks follow a minimum in P/Ca which is possibly caused by the uptake of phosphor by plankton.

These results suggest that A. excavata have potential as a promising tool for high resolution paleoenvironmental reconstructions of both intermediate and overlying surface water masses.

References

Schleinkofer N, Raddatz J, Evans D, Gerdes A, Flögel S, Voigt S, et al. Elemental to calcium ratios in the marine bivalve Acesta excavata: an archive for high-resolution paleoceanographic reconstructions of intermediate water masses. PLoS One. Submitted

How to cite: Schleinkofer, N., Raddatz, J., Evans, D., Gerdes, A., Voigt, S., and Wisshak, M.: Ba/Ca, P/Ca, Li/Ca and Mn/Ca ratios in the deep-sea bivalve Acesta excavata: Valuable tools to reconstruct plankton dynamics in cold-water coral ecosystems?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4724, https://doi.org/10.5194/egusphere-egu2020-4724, 2020.

EGU2020-18358 | Displays | SSP1.5